Changeset 15419

#2846: Fixed uncaught ObjectDisposedException in HiveJobManagerView.

• Caught a potential NullReferenceException in the HiveClient when ClearHiveClient is called asynchronous.
• Use Task.Run for HiveClient.Refresh instead of Begin/EndInvoke.
• Use await with try-catch to marshal back any uncaught exceptions back to the UI-thread where the exception is displayed instead of HL crashing.