Utility function ignores bad unitDefIDs

Author: SteelBlueZK

LuaRules/Utilities/unitTypeChecker.lua

@@ -60,7 +60,11 @@ local isComm = {}
 function Spring.Utilities.isComm(unitDefID)
 	if not isComm[unitDefID] then
 		local ud = UnitDefs[unitDefID]
-		isComm[unitDefID] = (ud.customParams.dynamic_comm or ud.customParams.commtype) and 1 or 0
+		if ud ~= nil then
+			isComm[unitDefID] = (ud.customParams.dynamic_comm or ud.customParams.commtype) and 1 or 0
+		else
+			isComm[unitDefID] = 0
+		end
 	end
 	return isComm[unitDefID] == 1
 end