GLib exceptions with mono 2.10

[Adam Reviczky]

Marshaling delete-event signal
Exception in Gtk# callback delegate
  Note: Applications can use GLib.ExceptionManager.UnhandledException to handle the exception.
System.NullReferenceException: Object reference not set to an instance of an object
  at GLib.GType.GetQualifiedName (System.String cname) [0x00000] in <filename unknown>:0
  at GLib.GType.LookupType (IntPtr typeid) [0x00000] in <filename unknown>:0
  at GLib.Value.get_Val () [0x00000] in <filename unknown>:0
  at GLib.SignalClosure.MarshalCallback (IntPtr raw_closure, IntPtr return_val, UInt32 n_param_vals, IntPtr param_values, IntPtr invocation_hint, IntPtr marshal_data) [0x00000] in <filename unknown>:0
   at GLib.ExceptionManager.RaiseUnhandledException(System.Exception e, Boolean is_terminal)
   at GLib.SignalClosure.MarshalCallback(IntPtr raw_closure, IntPtr return_val, UInt32 n_param_vals, IntPtr param_values, IntPtr invocation_hint, IntPtr marshal_data)
   at Gtk.Application.gtk_main()
   at Gtk.Application.Run()
   at Gui+MyWindow..ctor(System.String[] args)
   at Gui.main(System.String[] args)