Add the quest item to the finished list once used

diff --git a/Monomyth.lua b/Monomyth.lua
index 3799ecb..0c154c0 100644
--- a/Monomyth.lua
+++ b/Monomyth.lua
@@ -200,6 +200,7 @@ Monomyth:Register('BAG_UPDATE', function(bag, handled)
 				QueryQuestsCompleted()
 			elseif(not completedQuests[id]) then
 				UseContainerItem(bag, slot)
+				completedQuests[id] = true
 			end
 		end
 	end