FATAL error

 INFO  2013-12-10 17:13:17,578 3.1.115.255 [14] Skylabs.Lobby.Client [(null)] - Xmpp Closed
 FATAL 2013-12-10 17:13:23,781 3.1.115.255 [2] Octgn.OctgnApp [(null)] - UNHANDLED EXCEPTION
 System.AggregateException: A Task's exception(s) were not observed either by Waiting on the Task or accessing its Exception property. As a result, the unobserved exception was rethrown by the finalizer thread. ---> System.ArgumentException: Delegate to an instance method cannot have null 'this'.
   at System.MulticastDelegate.ThrowNullThisInDelegateToInstance()
   at Octgn.Utils.Sounds.Close() in c:\Program Files (x86)\Jenkins\workspace\OCTGN-Release\octgnFX\Octgn\Utils\Sounds.cs:line 129
   at Octgn.Program.Exit() in c:\Program Files (x86)\Jenkins\workspace\OCTGN-Release\octgnFX\Octgn\Program.cs:line 183
   at System.Threading.Tasks.Task.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.TaskExceptionHolder.Finalize()
---> (Inner Exception #0) System.ArgumentException: Delegate to an instance method cannot have null 'this'.
   at System.MulticastDelegate.ThrowNullThisInDelegateToInstance()
   at Octgn.Utils.Sounds.Close() in c:\Program Files (x86)\Jenkins\workspace\OCTGN-Release\octgnFX\Octgn\Utils\Sounds.cs:line 129
   at Octgn.Program.Exit() in c:\Program Files (x86)\Jenkins\workspace\OCTGN-Release\octgnFX\Octgn\Program.cs:line 183
   at System.Threading.Tasks.Task.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()<---