Use helper function to deal with nil arguments to formatted strings.

diff --git a/Ovale.lua b/Ovale.lua
index 2c71364..6d6f50c 100644
--- a/Ovale.lua
+++ b/Ovale.lua
@@ -17,6 +17,8 @@ local OvaleOptions = nil

 local format = string.format
 local pairs = pairs
+local select = select
+local tostring = tostring
 local wipe = table.wipe
 local API_GetTime = GetTime
 local API_RegisterAddonMessagePrefix = RegisterAddonMessagePrefix
@@ -27,6 +29,10 @@ local API_UnitHasVehicleUI = UnitHasVehicleUI
 local API_UnitIsDead = UnitIsDead

 local self_damageMeterMethods = {}
+
+local OVALE_FALSE_STRING = tostring(false)
+local OVALE_NIL_STRING = tostring(nil)
+local OVALE_TRUE_STRING = tostring(true)
 --</private-static-properties>

 --<public-static-properties>
@@ -66,6 +72,20 @@ BINDING_NAME_OVALE_CHECKBOX3 = L["Inverser la boîte à cocher "].."(4)"
 BINDING_NAME_OVALE_CHECKBOX4 = L["Inverser la boîte à cocher "].."(5)"

 --<private-static-methods>
+-- format() wrapper that turns nil arguments into tostring(nil)
+local function Format(...)
+	local arg = {}
+	for i = 1, select("#", ...) do
+		local v = select(i, ...)
+		if type(v) == "boolean" then
+			arg[i] = v and OVALE_TRUE_STRING or OVALE_FALSE_STRING
+		else
+			arg[i] = v or OVALE_NIL_STRING
+		end
+	end
+	return format(unpack(arg))
+end
+
 local function OnCheckBoxValueChanged(widget)
 	OvaleOptions:GetProfile().check[widget.userdata.k] = widget:GetValue()
 	if Ovale.casesACocher[widget.userdata.k].compile then
@@ -293,6 +313,10 @@ function Ovale:SendScoreToDamageMeter(name, guid, scored, scoreMax)
 end

 -- Debugging methods.
+function Ovale:FormatPrint(...)
+	self:Print(Format(...))
+end
+
 function Ovale:DebugPrint(flag, ...)
 	local profile = OvaleOptions:GetProfile()
 	if profile and profile.debug and profile.debug[flag] then
@@ -303,7 +327,7 @@ end
 function Ovale:DebugPrintf(flag, ...)
 	local profile = OvaleOptions:GetProfile()
 	if profile and profile.debug and profile.debug[flag] then
-		self:Printf("[%s] %s", flag, format(...))
+		self:Printf("[%s] %s", flag, Format(...))
 	end
 end

@@ -313,7 +337,7 @@ function Ovale:Error(...)
 end

 function Ovale:Errorf(...)
-	self:Printf("Fatal error: %s", format(...))
+	self:Printf("Fatal error: %s", Format(...))
 	self.bug = true
 end

@@ -325,7 +349,7 @@ end

 function Ovale:Logf(...)
 	if self.trace then
-		return self:Printf(...)
+		return self:Printf(Format(...))
 	end
 end
 --</public-static-methods>
diff --git a/OvaleAura.lua b/OvaleAura.lua
index a34d1a2..037a1e7 100644
--- a/OvaleAura.lua
+++ b/OvaleAura.lua
@@ -439,7 +439,7 @@ function OvaleAura:Debug()
 		for filter, auraList in pairs(auraTable) do
 			for spellId, whoseTable in pairs(auraList) do
 				for whose, aura in pairs(whoseTable) do
-					Ovale:Printf("%s %s %s %s %s stacks=%d tick=%s", guid, filter, whose, spellId, aura.name, aura.stacks, aura.tick)
+					Ovale:FormatPrint("%s %s %s %s %s stacks=%d tick=%s", guid, filter, whose, spellId, aura.name, aura.stacks, aura.tick)
 				end
 			end
 		end
diff --git a/OvaleBestAction.lua b/OvaleBestAction.lua
index 4d4bf08..98bb9f1 100644
--- a/OvaleBestAction.lua
+++ b/OvaleBestAction.lua
@@ -295,10 +295,10 @@ local function ComputeFunction(element)
 		if Ovale.trace then
 			local conditionCall = element.func .. "("
 			for k, v in pairs(element.params) do
-				conditionCall = parameterList .. k .. "=" .. v .. ","
+				conditionCall = conditionCall .. k .. "=" .. v .. ","
 			end
 			conditionCall = conditionCall .. ")"
-			Ovale:Printf("Condition %s returned %s, %s, %s, %s, %s", conditionCall, start, ending, value, origin, rate)
+			Ovale:FormatPrint("Condition %s returned %s, %s, %s, %s, %s", conditionCall, start, ending, value, origin, rate)
 		end

 		if value then
diff --git a/OvaleComboPoints.lua b/OvaleComboPoints.lua
index 349f3b7..a556729 100644
--- a/OvaleComboPoints.lua
+++ b/OvaleComboPoints.lua
@@ -81,6 +81,6 @@ function OvaleComboPoints:Refresh()
 end

 function OvaleComboPoints:Debug()
-	Ovale:Printf("Player has %d combo points on target %s.", self.combo, OvaleGUID:GetGUID("target"))
+	Ovale:FormatPrint("Player has %d combo points on target %s.", self.combo, OvaleGUID:GetGUID("target"))
 end
 --</public-static-methods>
diff --git a/OvaleCompile.lua b/OvaleCompile.lua
index 7d31024..5d74a86 100644
--- a/OvaleCompile.lua
+++ b/OvaleCompile.lua
@@ -99,7 +99,7 @@ local function HasTalent(talentId)
 		if OvaleData.pointsTalent[talentId]~=nil then
 			return OvaleData.pointsTalent[talentId]>0
 		else
-			Ovale:Printf("Unknown talent %s", talentId)
+			Ovale:FormatPrint("Unknown talent %s", talentId)
 			return false
 		end
 	else
@@ -329,10 +329,10 @@ local function ParseScoreSpells(params)
 	for v in strgmatch(params, "(%d+)") do
 		local spellId = tonumber(v)
 		if spellId then
-			--Ovale:Printf("Add spell to score %d", spellId)
+			--Ovale:FormatPrint("Add spell to score %d", spellId)
 			OvaleData.scoreSpell[spellId] = true
 		else
-			Ovale:Printf("ScoreSpell with unknown spell %s", v)
+			Ovale:FormatPrint("ScoreSpell with unknown spell %s", v)
 		end
 	end
 end
@@ -461,7 +461,7 @@ local function ParseGroup(text)
 	text = strgsub(text, "node%d+", "")

 	if (strmatch(text,"[^ ]")) then
-		Ovale:Printf("syntax error: %s", text)
+		Ovale:FormatPrint("syntax error: %s", text)
 		return nil
 	end

@@ -586,8 +586,8 @@ local function ParseCommands(text)
 	-- Si il reste autre chose que des espaces, c'est une erreur de syntaxe
 	text = strgsub(text, "node%d+", "", 1)
 	if strmatch(text,"[^ ]") then
-		Ovale:Printf("Group: %s", original)
-		Ovale:Printf("syntax error: %s", text)
+		Ovale:FormatPrint("Group: %s", original)
+		Ovale:FormatPrint("syntax error: %s", text)
 		return nil
 	end
 	return masterNode
@@ -611,7 +611,7 @@ local function ParseCanStopChannelling(text)
 	if spellId then
 		OvaleData:GetSpellInfo(spellId).canStopChannelling = true
 	else
-		Ovale:Printf("CanStopChannelling with unknown spell %s", text)
+		Ovale:FormatPrint("CanStopChannelling with unknown spell %s", text)
 	end
 	return ""
 end
@@ -622,7 +622,7 @@ local function ParseItemName(text)
 		local item = API_GetItemInfo(spellId) or "Item " .. itemId
 		return '"' .. item .. '"'
 	else
-		Ovale:Printf("ItemName of %s unknown\n", text)
+		Ovale:FormatPrint("ItemName of %s unknown\n", text)
 		return nil
 	end
 end
@@ -633,7 +633,7 @@ local function ParseSpellName(text)
 	if spell then
 		return '"' .. spell .. '"'
 	else
-		Ovale:Printf("SpellName of %s unknown", text)
+		Ovale:FormatPrint("SpellName of %s unknown", text)
 		return nil
 	end
 end
diff --git a/OvaleEnemies.lua b/OvaleEnemies.lua
index 37f8ae0..a364295 100644
--- a/OvaleEnemies.lua
+++ b/OvaleEnemies.lua
@@ -126,7 +126,7 @@ end

 function OvaleEnemies:Debug()
 	for guid, timestamp in pairs(self_enemyLastSeen) do
-		Ovale:Printf("enemy %s (%s) last seen at %f", guid, self_enemyName[guid], timestamp)
+		Ovale:FormatPrint("enemy %s (%s) last seen at %f", guid, self_enemyName[guid], timestamp)
 	end
 end
 --</public-static-methods>
diff --git a/OvaleEquipement.lua b/OvaleEquipement.lua
index 18fba02..54e5262 100644
--- a/OvaleEquipement.lua
+++ b/OvaleEquipement.lua
@@ -1065,12 +1065,12 @@ end

 function OvaleEquipement:Debug()
 	for slotId = INVSLOT_FIRST_EQUIPPED, INVSLOT_LAST_EQUIPPED do
-		Ovale:Printf("Slot %d = %s", slotId, self:GetEquippedItem(slotId))
+		Ovale:FormatPrint("Slot %d = %s", slotId, self:GetEquippedItem(slotId))
 	end
-	Ovale:Printf("Main-hand item type: %s", self_mainHandItemType)
-	Ovale:Printf("Off-hand item type: %s", self_offHandItemType)
+	Ovale:FormatPrint("Main-hand item type: %s", self_mainHandItemType)
+	Ovale:FormatPrint("Off-hand item type: %s", self_offHandItemType)
 	for k, v in pairs(self_armorSetCount) do
-		Ovale:Printf("Player has %d piece(s) of %s armor set.", v, k)
+		Ovale:FormatPrint("Player has %d piece(s) of %s armor set.", v, k)
 	end
 end
 --</public-static-methods>
diff --git a/OvaleFuture.lua b/OvaleFuture.lua
index 9021ae3..5b93a02 100644
--- a/OvaleFuture.lua
+++ b/OvaleFuture.lua
@@ -85,14 +85,14 @@ local function AddSpellToQueue(spellId, lineId, startTime, endTime, channeled, a
 	spellcast.allowRemove = allowRemove
 	--TODO unable to know what is the real target
 	if lineId == self_lastLineID and self_lastTarget then
-		-- Ovale:Printf("found lineId %d, target is %s", lineId, self_lastTarget)
+		-- Ovale:FormatPrint("found lineId %d, target is %s", lineId, self_lastTarget)
 		spellcast.target = self_lastTarget
 	else
 		spellcast.target = API_UnitGUID("target")
 	end
 	if self.traceSpellId and self.traceSpellId == spellId then
-		Ovale:Printf("    AddSpellToQueue: %f %s (%d), lineId = %d", Ovale.now, OvaleData:GetSpellName(spellId), spellId, lineId)
-		Ovale:Printf("        startTime = %f, endTime = %f, target = %s", startTime, endTime, spellcast.target)
+		Ovale:FormatPrint("    AddSpellToQueue: %f %s (%d), lineId = %d", Ovale.now, OvaleData:GetSpellName(spellId), spellId, lineId)
+		Ovale:FormatPrint("        startTime = %f, endTime = %f, target = %s", startTime, endTime, spellcast.target)
 	end

 	-- Snapshot the current stats for the spellcast.
@@ -155,7 +155,7 @@ local function RemoveSpellFromQueue(spellId, lineId)
 	for index, spellcast in ipairs(self_activeSpellcast) do
 		if spellcast.lineId == lineId then
 			if self.traceSpellId and self.traceSpellId == spellId then
-				Ovale:Printf("    RemoveSpellFromQueue: %f %s (%d)", Ovale.now, OvaleData:GetSpellName(spellId), spellId)
+				Ovale:FormatPrint("    RemoveSpellFromQueue: %f %s (%d)", Ovale.now, OvaleData:GetSpellName(spellId), spellId)
 			end
 			tremove(self_activeSpellcast, index)
 			self_pool:Release(spellcast)
@@ -192,8 +192,8 @@ function OvaleFuture:UNIT_SPELLCAST_CHANNEL_START(event, unit, name, rank, lineI
 	if unit == "player" then
 		local startTime, endTime = select(5, API_UnitChannelInfo("player"))
 		if self.traceSpellId and self.traceSpellId == spellId then
-			Ovale:Printf("%s: %f %s (%d), lineId = %d", event, Ovale.now, spellName, spellId, lineId)
-			Ovale:Printf("    startTime = %f, endTime = %f", startTime, endTime)
+			Ovale:FormatPrint("%s: %f %s (%d), lineId = %d", event, Ovale.now, spellName, spellId, lineId)
+			Ovale:FormatPrint("    startTime = %f, endTime = %f", startTime, endTime)
 		end
 		AddSpellToQueue(spellId, lineId, startTime/1000, endTime/1000, true, false)
 	end
@@ -202,7 +202,7 @@ end
 function OvaleFuture:UNIT_SPELLCAST_CHANNEL_STOP(event, unit, name, rank, lineId, spellId)
 	if unit == "player" then
 		if self.traceSpellId and self.traceSpellId == spellId then
-			Ovale:Printf("%s: %f %s (%d), lineId = %d", event, Ovale.now, spellName, spellId, lineId)
+			Ovale:FormatPrint("%s: %f %s (%d), lineId = %d", event, Ovale.now, spellName, spellId, lineId)
 		end
 		RemoveSpellFromQueue(spellId, lineId)
 	end
@@ -213,8 +213,8 @@ function OvaleFuture:UNIT_SPELLCAST_START(event, unit, name, rank, lineId, spell
 	if unit == "player" then
 		local startTime, endTime = select(5, API_UnitCastingInfo("player"))
 		if self.traceSpellId and self.traceSpellId == spellId then
-			Ovale:Printf("%s: %f %s (%d), lineId = %d", event, Ovale.now, spellName, spellId, lineId)
-			Ovale:Printf("    startTime = %f, endTime = %f", startTime, endTime)
+			Ovale:FormatPrint("%s: %f %s (%d), lineId = %d", event, Ovale.now, spellName, spellId, lineId)
+			Ovale:FormatPrint("    startTime = %f, endTime = %f", startTime, endTime)
 		end
 		AddSpellToQueue(spellId, lineId, startTime/1000, endTime/1000, false, false)
 	end
@@ -224,7 +224,7 @@ end
 function OvaleFuture:UNIT_SPELLCAST_INTERRUPTED(event, unit, name, rank, lineId, spellId)
 	if unit == "player" then
 		if self.traceSpellId and self.traceSpellId == spellId then
-			Ovale:Printf("%s: %f %s (%d), lineId = %d", event, Ovale.now, spellName, spellId, lineId)
+			Ovale:FormatPrint("%s: %f %s (%d), lineId = %d", event, Ovale.now, spellName, spellId, lineId)
 		end
 		RemoveSpellFromQueue(spellId, lineId)
 	end
@@ -245,8 +245,8 @@ function OvaleFuture:UNIT_SPELLCAST_SENT(event, unit, spell, rank, target, lineI
 		self_lastTarget = targetGUID
 		self_lastLineID = lineId
 		if self.traceSpellId and self.traceSpellId == spellId then
-			Ovale:Printf("%s: %f %s (%d), lineId = %d", event, Ovale.now, spellName, spellId, lineId)
-			Ovale:Printf("    targetGUID = %s", targetGUID)
+			Ovale:FormatPrint("%s: %f %s (%d), lineId = %d", event, Ovale.now, spellName, spellId, lineId)
+			Ovale:FormatPrint("    targetGUID = %s", targetGUID)
 		end
 		for _, spellcast in ipairs(self_activeSpellcast) do
 			if spellcast.lineId == lineId then
@@ -259,7 +259,7 @@ end
 function OvaleFuture:UNIT_SPELLCAST_SUCCEEDED(event, unit, name, rank, lineId, spellId)
 	if unit == "player" then
 		if self.traceSpellId and self.traceSpellId == spellId then
-			Ovale:Printf("%s: %f %s (%d), lineId = %d", event, Ovale.now, spellName, spellId, lineId)
+			Ovale:FormatPrint("%s: %f %s (%d), lineId = %d", event, Ovale.now, spellName, spellId, lineId)
 		end
 		-- Search for a cast-time spell matching this spellcast that was added by UNIT_SPELLCAST_START.
 		for _, spellcast in ipairs(self_activeSpellcast) do
@@ -334,13 +334,13 @@ function OvaleFuture:COMBAT_LOG_EVENT_UNFILTERED(event, ...)
 				or strfind(event, "SPELL_MISSED") == 1 then
 			local spellId, spellName = select(12, ...)
 			if self.traceSpellId and self.traceSpellId == spellId then
-				Ovale:Printf("%s: %f %s (%d), lineId = %d", event, Ovale.now, spellName, spellId, lineId)
+				Ovale:FormatPrint("%s: %f %s (%d), lineId = %d", event, Ovale.now, spellName, spellId, lineId)
 			end
 			for index, spellcast in ipairs(self_activeSpellcast) do
 				if spellcast.allowRemove and (spellcast.spellId == spellId or spellcast.auraSpellId == spellId) then
 					if not spellcast.channeled and (spellcast.removeOnSuccess or strfind(event, "SPELL_CAST_SUCCESS") ~= 1) then
 						if self.traceSpellId and self.traceSpellId == spellId then
-							Ovale:Printf("    Spell finished: %f %s (%d)", Ovale.now, OvaleData:GetSpellName(spellId), spellId)
+							Ovale:FormatPrint("    Spell finished: %f %s (%d)", Ovale.now, OvaleData:GetSpellName(spellId), spellId)
 						end
 						tremove(self_activeSpellcast, index)
 						self_pool:Release(spellcast)
@@ -428,7 +428,7 @@ function OvaleFuture:Debug()
 		Ovale:Print("No spells in flight!")
 	end
 	for spellId, lineId in self:InFlightSpells(Ovale.now) do
-		Ovale:Printf("    %s (%d), lineId = %s", OvaleData:GetSpellName(spellId), spellId, lineId)
+		Ovale:FormatPrint("    %s (%d), lineId = %s", OvaleData:GetSpellName(spellId), spellId, lineId)
 	end
 end
 --</public-static-methods>
diff --git a/OvaleGUID.lua b/OvaleGUID.lua
index bb015cf..044dad6 100644
--- a/OvaleGUID.lua
+++ b/OvaleGUID.lua
@@ -56,7 +56,7 @@ function OvaleGUID:OnDisable()
 end

 function OvaleGUID:Update(unitId)
-	--self:Printf("OvaleGUID:Update %s", unitId)
+	--self:FormatPrint("OvaleGUID:Update %s", unitId)
 	local guid = API_UnitGUID(unitId)
 	local previousGuid = self_guid[unitId]
 	if previousGuid ~= guid then
diff --git a/OvaleIcone.lua b/OvaleIcone.lua
index cef6daa..865facb 100644
--- a/OvaleIcone.lua
+++ b/OvaleIcone.lua
@@ -199,7 +199,7 @@ local function SetParams(self, params, secure)
 				local prefix = strsub(k, 1, f-1)
 				local suffix = strsub(k, f + 5)
 				local param
-				Ovale:Printf("%stype%s", prefix, suffix)
+				Ovale:FormatPrint("%stype%s", prefix, suffix)
 				self:SetAttribute(prefix .. "type" .. suffix, "spell")
 				self:SetAttribute("unit", self.params.target or "target")
 				self:SetAttribute(k, OvaleData.spellList[v])
diff --git a/OvalePaperDoll.lua b/OvalePaperDoll.lua
index 2f00dbd..1265018 100644
--- a/OvalePaperDoll.lua
+++ b/OvalePaperDoll.lua
@@ -202,21 +202,21 @@ function OvalePaperDoll:GetSpellHasteMultiplier()
 end

 function OvalePaperDoll:Debug()
-	Ovale:Printf("Class: %s", self.class)
-	Ovale:Printf("Level: %d", self.level)
-	Ovale:Printf("Specialization: %s", self.specialization)
-	Ovale:Printf("Agility: %d", self.agility)
-	Ovale:Printf("Intellect: %d", self.intellect)
-	Ovale:Printf("Spirit: %d", self.spirit)
-	Ovale:Printf("Stamina: %d", self.stamina)
-	Ovale:Printf("Strength: %d", self.strength)
-	Ovale:Printf("AP: %d", self.attackPower)
-	Ovale:Printf("RAP: %d", self.rangedAttackPower)
-	Ovale:Printf("Spell bonus damage: %d", self.spellBonusDamage)
-	Ovale:Printf("Spell bonus healing: %d", self.spellBonusHealing)
-	Ovale:Printf("Spell haste effect: %f%%", self.spellHaste)
-	Ovale:Printf("Melee haste effect: %f%%", self.meleeHaste)
-	Ovale:Printf("Ranged haste effect: %f%%", self.rangedHaste)
-	Ovale:Printf("Mastery effect: %f%%", self.masteryEffect)
+	Ovale:FormatPrint("Class: %s", self.class)
+	Ovale:FormatPrint("Level: %d", self.level)
+	Ovale:FormatPrint("Specialization: %s", self.specialization)
+	Ovale:FormatPrint("Agility: %d", self.agility)
+	Ovale:FormatPrint("Intellect: %d", self.intellect)
+	Ovale:FormatPrint("Spirit: %d", self.spirit)
+	Ovale:FormatPrint("Stamina: %d", self.stamina)
+	Ovale:FormatPrint("Strength: %d", self.strength)
+	Ovale:FormatPrint("AP: %d", self.attackPower)
+	Ovale:FormatPrint("RAP: %d", self.rangedAttackPower)
+	Ovale:FormatPrint("Spell bonus damage: %d", self.spellBonusDamage)
+	Ovale:FormatPrint("Spell bonus healing: %d", self.spellBonusHealing)
+	Ovale:FormatPrint("Spell haste effect: %f%%", self.spellHaste)
+	Ovale:FormatPrint("Melee haste effect: %f%%", self.meleeHaste)
+	Ovale:FormatPrint("Ranged haste effect: %f%%", self.rangedHaste)
+	Ovale:FormatPrint("Mastery effect: %f%%", self.masteryEffect)
 end
 --</public-static-methods>
diff --git a/OvalePool.lua b/OvalePool.lua
index 7e51e09..925bf93 100644
--- a/OvalePool.lua
+++ b/OvalePool.lua
@@ -57,6 +57,6 @@ function OvalePool:Drain()
 end

 function OvalePool:Debug()
-	Ovale:Printf("Pool %s has size %d with %d item(s).", self.name, self.size, self.unused)
+	Ovale:FormatPrint("Pool %s has size %d with %d item(s).", self.name, self.size, self.unused)
 end
 --</public-static-methods>
diff --git a/OvaleStance.lua b/OvaleStance.lua
index 2741b42..7a6d8c2 100644
--- a/OvaleStance.lua
+++ b/OvaleStance.lua
@@ -129,7 +129,7 @@ function OvaleStance:DebugStances()
 end

 function OvaleStance:Debug()
-	Ovale:Printf("current stance: %s", self_stance)
+	Ovale:FormatPrint("current stance: %s", self_stance)
 end

 -- Return true if the current stance matches the given name.