Clipboard isn't working

[Eslam Mostafa]

Cut, copy, paste functions raise error:

(txtr:8619): Gtk-CRITICAL **: gtk_widget_add_events: assertion `GTK_IS_WIDGET (widget)' failed
/usr/lib/python2.7/dist-packages/gi/types.py:43: Warning: g_object_set_data: assertion `G_IS_OBJECT (object)' failed
  return info.invoke(*args, **kwargs)

(txtr:8619): Gdk-CRITICAL **: gdk_display_get_default_screen: assertion `GDK_IS_DISPLAY (display)' failed

(txtr:8619): Gtk-CRITICAL **: gtk_invisible_new_for_screen: assertion `GDK_IS_SCREEN (screen)' failed

(txtr:8619): Gtk-CRITICAL **: gtk_widget_add_events: assertion `GTK_IS_WIDGET (widget)' failed

(txtr:8619): Gtk-CRITICAL **: gtk_selection_owner_set_for_display: assertion `GDK_IS_DISPLAY (display)' failed

(txtr:8619): Gdk-CRITICAL **: gdk_display_supports_clipboard_persistence: assertion `GDK_IS_DISPLAY (display)' failed