(MonoDevelop:6548): GLib-GObject-CRITICAL **: g_object_ref: assertion `object->ref_count > 0' failed

(MonoDevelop:6548): Gtk-CRITICAL **: gtk_toolbar_remove: assertion `content_to_remove != NULL' failed

(MonoDevelop:6548): Gtk-CRITICAL **: gtk_toolbar_remove: assertion `content_to_remove != NULL' failed
System.NullReferenceException: Object reference not set to an instance of an object
  at MonoDevelop.GtkCore.WidgetLibrary.ProjectClassDescriptor.MakeChildrenUnselectable (Gtk.Widget w) [0x00000]
  at MonoDevelop.GtkCore.WidgetLibrary.ProjectClassDescriptor.MakeChildrenUnselectable (Gtk.Widget w) [0x00000]
  at MonoDevelop.GtkCore.WidgetLibrary.ProjectClassDescriptor.MakeChildrenUnselectable (Gtk.Widget w) [0x00000]
  at MonoDevelop.GtkCore.WidgetLibrary.ProjectClassDescriptor.MakeChildrenUnselectable (Gtk.Widget w) [0x00000]
  at MonoDevelop.GtkCore.WidgetLibrary.ProjectClassDescriptor.CreateInstance (IProject proj) [0x00000]
  at Stetic.ClassDescriptor.NewInstance (IProject proj) [0x00000]
  at Stetic.WidgetFactory.CreateItemWidget () [0x00000]
  at Stetic.PaletteItemFactory.OnDragBegin (Gdk.DragContext ctx) [0x00000]
  at Gtk.Widget.dragbegin_cb (IntPtr widget, IntPtr context) [0x00000]
  at (wrapper native-to-managed) Gtk.Widget:dragbegin_cb (intptr,intptr)
  at <0x00000> <unknown method>
  at (wrapper managed-to-native) Gtk.Application:gtk_main ()
  at Gtk.Application.Run () [0x00000]
  at MonoDevelop.Ide.Gui.IdeApp.Run () [0x00000]
  at MonoDevelop.Ide.Gui.IdeStartup.Run (System.String[] args) [0x00000]
  at MonoDevelop.Core.AddIns.AddInService.StartApplication (System.String addinId, System.String[] parameters) [0x00000]