Core/Items: Items shouldn't have a negative item level

Closes #11631

src/server/game/Entities/Item/ItemPrototype.h

@@ -734,7 +734,7 @@ struct ItemTemplate
             default:
                 break;
         }
-        return itemLevel;
+        return std::max<float>(0.f, itemLevel);
     }
 
     bool IsPotion() const { return Class == ITEM_CLASS_CONSUMABLE && SubClass == ITEM_SUBCLASS_POTION; }