Fixed a nil error when an item is acquired.

diff --git a/CauldronMain.lua b/CauldronMain.lua
index dd603bb..d67e062 100644
--- a/CauldronMain.lua
+++ b/CauldronMain.lua
@@ -387,7 +387,7 @@ function Cauldron:OnBagUpdate(event, bagid)
 			-- adjust queue, but only if window is open
 			self:debug("adjust queue? item="..item);
 			if CauldronFrame:IsShown() then
-				self:debug("window is open; self.makingItem="..self.makingItem);
+				self:debug("window is open; self.makingItem="..tostring(self.makingItem));
 				if self.makingItem == item then
 					self:debug("OnBagUpdate: adjust queue for item: "..self.makingItem.."; itemCount="..itemCount);
 					CauldronQueue:AdjustItemCount(queue, item, -itemCount);