Argument cannot be null.
Parameter name: type
  at System.Activator.CheckType (System.Type type) [0x00000] in <filename unknown>:0
  at System.Activator.CreateInstance (System.Type type, Boolean nonPublic) [0x00000] in <filename unknown>:0
  at System.Activator.CreateInstance (System.Type type) [0x00000] in <filename unknown>:0
  at Verse.ThingMaker.MakeThing (Verse.ThingDef def, Verse.ThingDef stuff) [0x00000] in <filename unknown>:0
  at RimWorld.Designator_Build.DesignateSingleCell (IntVec3 c) [0x00000] in <filename unknown>:0
  at Verse.Designator.DesignateMultiCell (IEnumerable`1 cells) [0x00000] in <filename unknown>:0
  at Verse.DesignatorManager.ProcessInputEvents () [0x00000] in <filename unknown>:0
  at RimWorld.MapInterface.HandleMapClicks () [0x00000] in <filename unknown>:0
  at RimWorld.UIRoot_Play.UIRootOnGUI () [0x00000] in <filename unknown>:0
  at Verse.Root.OnGUI () [0x00000] in <filename unknown>:0