求哪位大神知道这是什么BUG吗？

markohcf

System.NullReferenceException: Object reference not set to an instance of an object
  at RimWorld.SkillRecord.Interval () [0x00000] in <filename unknown>:0
  at RimWorld.Pawn_SkillTracker.SkillsTick () [0x00000] in <filename unknown>:0
  at Verse.Pawn.Tick () [0x00000] in <filename unknown>:0
  at RimWorld.Planet.WorldPawns.WorldPawnsTick () [0x00000] in <filename unknown>:0
  at RimWorld.Planet.World.WorldTick () [0x00000] in <filename unknown>:0
  at Verse.TickManager.DoSingleTick () [0x00000] in <filename unknown>:0
Verse.Log:Error(String)
Verse.TickManageroSingleTick()
Verse.TickManager:TickManagerUpdate()
Verse.Game:Update()
Verse.Root_Play:Update()