Is spammed into the console, does anyone know why or what it is?

NullReferenceException: Object reference not set to an instance of an object
at ConsoleSystem.Internal (ConsoleSystem+Arg arg) [0x0005b] in <2c374720c7c94eebb17a7d75fb8584ee>:0
UnityEngine.DebugLogHandler:Internal_LogException(Exception, Object)
UnityEngine.DebugLogHandler:LogException(Exception, Object)
UnityEngine.Logger:LogException(Exception, Object)
UnityEngine.Debug:LogException(Exception)
ConsoleSystem:Internal(Arg)
ConsoleSystem:Run(Option, String, Object[])
Facepunch.RCon:OnCommand(Command)
Facepunch.RCon:Update()
SaveRestore:Load(String, Boolean)
ServerMgr:Initialize(Boolean, String, Boolean, Boolean)
<StartServer>d__21:MoveNext()
UnityEngine.SetupCoroutine:InvokeMoveNext(IEnumerator, IntPtr)