Exception right after deconstructed curtain

[jinlan]

Exception ticking HeronInvisibleDoor76688: System.NullReferenceException: Object reference not set to an instance of an object
  at Verse.GridsUtility.GetThingList (IntVec3 c, Verse.Map map) [0x00000] in <filename unknown>:0 
  at RimWorld.Building_Door.Tick () [0x00000] in <filename unknown>:0 
  at DoorsExpanded.Building_DoorRegionHandler.Tick () [0x00000] in <filename unknown>:0 
  at Verse.TickList.Tick () [0x00000] in <filename unknown>:0 
Verse.Log:Error(String, Boolean)
Verse.TickList:Tick()
Verse.TickManager:DoSingleTick()
Verse.TickManager:TickManagerUpdate()
Verse.Game:UpdatePlay()
Verse.Root_Play:Update()