4.16 ver
[2017.08.06-18.26.03:500] 0]LogProperty:Warning: Serialized Class /Script/CoreUObject.LinkerPlaceholderExportObject for a property of WidgetBlueprintGeneratedClass /Game/MMO/Blueprints/Inventory/InventorySlot.InventorySlot_C. Reference will be NULLed.