Core/Loot: Fixed looting creatures that have only quest items in their loot

Closes #12400

src/server/game/Entities/Unit/Unit.cpp

@@ -15393,7 +15393,7 @@ void Unit::Kill(Unit* victim, bool durabilityLoss)
             creature->DeleteThreatList();
 
             // must be after setDeathState which resets dynamic flags
-            if (!creature->loot.empty())
+            if (!creature->loot.isLooted())
                 creature->SetFlag(UNIT_DYNAMIC_FLAGS, UNIT_DYNFLAG_LOOTABLE);
             else
                 creature->AllLootRemovedFromCorpse();