Exception in Gtk# callback delegate
  Note: Applications can use GLib.ExceptionManager.UnhandledException to handle the exception.
System.NullReferenceException: A null value was found where an object instance was required.
  at Do.Addins.UI.MiniWindow.SetPaneContext (Pane pane, Do.Addins.SearchContext context) [0x00000] 
  at Do.Core.Controller.OnTabKeyPressEvent (Gdk.EventKey evnt) [0x00000] 
  at Do.Core.Controller.KeyPressWrap (Gdk.EventKey evnt) [0x00000] 
  at (wrapper delegate-invoke) System.MulticastDelegate:invoke_void_EventKey (Gdk.EventKey)
  at Do.Addins.UI.MiniWindow.OnKeyPressEvent (Gdk.EventKey evnt) [0x00000] 
  at Gtk.Widget.keypressevent_cb (IntPtr widget, IntPtr evnt) [0x00000] 

   at GLib.ExceptionManager.RaiseUnhandledException ()
   at Gtk.Widget.keypressevent_cb ()
   at Gtk.Widget.keypressevent_cb ()
   at Gtk.Application.gtk_main ()
   at Gtk.Application.gtk_main ()
   at Gtk.Application.Run ()
   at Do.Do.Main ()