Object reference not set to an instance of an object [System.NullReferenceException]

Details:
No details
System.NullReferenceException: Object reference not set to an instance of an object
  at TouristAI.StartPathFind (UInt16 instanceID, .CitizenInstance& citizenData) [0x00000] in <filename unknown>:0
  at TouristAI.SetTarget (UInt16 instanceID, .CitizenInstance& data, UInt16 targetBuilding) [0x00000] in <filename unknown>:0
  at BuildingManager.ReleaseBuildingImplementation (UInt16 building, .Building& data) [0x00000] in <filename unknown>:0
  at BuildingManager.ReleaseBuilding (UInt16 building) [0x00000] in <filename unknown>:0
  at BuildingManager.UpdateData (UpdateMode mode) [0x00000] in <filename unknown>:0
  at SimulationManager.Managers_UpdateData (UpdateMode mode, Single minProgress, Single maxProgress) [0x00000] in <filename unknown>:0
  at LoadingManager+<LoadSimulationData>c__Iterator57.MoveNext () [0x00000] in <filename unknown>:0
  at AsyncTask.Execute () [0x00000] in <filename unknown>:0