coa.18: guard DataStore_Achievements nil criteria quantity

GetAchievementCriteriaInfo returns nil reqQuantity/quantity for some CoA achievements;
'reqQuantity > 1' crashed. Guarded both.

Altoholic/Altoholic.toc

@@ -13,7 +13,7 @@
 
 ## Author: Thaoky, Telkar-RG
 ## X-Edited-By: Exiles (Sub-Net) — florian.berthold@sub-net.at
-## Version: 3.3.002b-coa.17
+## Version: 3.3.002b-coa.18
 ## X-Category: Inventory, Tradeskill, Mail
 ## X-Localizations: enUS, frFR, zhCN, zhTW, deDE, koKR, esES, esMX, ruRU
 ## X-Website: http://wow.curse.com/downloads/wow-addons/details/altoholic.aspx

DataStore_Achievements/DataStore_Achievements.lua

@@ -55,8 +55,8 @@ local function ScanSingleAchievement(id, isCompleted, month, day, year)
 	   if critCompleted then 
 	      table.insert(CriteriaCache, tostring(j))
 	   else                  
-	      if reqQuantity > 1 then
-	         table.insert(CriteriaCache, j .. ":" .. quantity)
+	      if (reqQuantity or 0) > 1 then		-- CoA: GetAchievementCriteriaInfo can return nil quantities for custom/partial achievements
+	         table.insert(CriteriaCache, j .. ":" .. (quantity or 0))
 	      end
 	   end
 	end