try to fix guild dt. This closes #273

diff --git a/ElvUI_SLE/modules/sledatatexts/guild.lua b/ElvUI_SLE/modules/sledatatexts/guild.lua
index 016f3de..d84438b 100644
--- a/ElvUI_SLE/modules/sledatatexts/guild.lua
+++ b/ElvUI_SLE/modules/sledatatexts/guild.lua
@@ -69,7 +69,9 @@ local list_sort = {
 		end
 	end,
 	ZONENAME = function(a, b)
-		if a["ZONENAME"] < b["ZONENAME"] then
+		if not a["ZONENAME"] or not b["ZONENAME"] then
+			return false
+		elseif a["ZONENAME"] < b["ZONENAME"] then
 			return true
 		elseif a["ZONENAME"] > b["ZONENAME"] then
 			return false