Created Unassigned: Null Exception thrown inside library [2721]

Below exception crashes the windows app. Any Ideas what is cause of the problem here.

Thanks.
```
Application: MyApp.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.NullReferenceException
Stack:
at Renci.SshNet.Sftp.SubsystemSession.RaiseError(System.Exception)
at System.EventHandler`1[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]].Invoke(System.Object, System.__Canon)
at Renci.SshNet.Session.RaiseError(System.Exception)
at Renci.SshNet.Session.MessageListener()
at Renci.SshNet.Session.<Connect>b__4()
at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
at System.Threading.ThreadPoolWorkQueue.Dispatch()

```