NullReferenceException at JunkPile.ServerInit

Code:

(21:46:41) | System.NullReferenceException: Object reference not set to an instance of an object
  at JunkPile.ServerInit () [0x00000] in <filename unknown>:0
  at BaseNetworkable.Spawn () [0x00000] in <filename unknown>:0
  at SpawnHandler.Spawn (.SpawnPopulation population, .SpawnDistribution distribution, Vector3 pos, Quaternion rot) [0x00000] in <filename unknown>:0
  at SpawnHandler.Spawn (.SpawnPopulation population, .SpawnDistribution distribution, Int32 targetCount, Int32 numToFill, Int32 numToTry) [0x00000] in <filename unknown>:0
  at SpawnHandler.SpawnRepeating (.SpawnPopulation population, .SpawnDistribution distribution) [0x00000] in <filename unknown>:0
  at SpawnHandler+<SpawnTick>c__Iterator0.MoveNext () [0x00000] in <filename unknown>:0

 

same error messgae