[mutter] display: Unref selection on shutdown

[Robert Mader <rmader src gnome org>]

commit d699c80ac2531d21ba757ac5f21082a4786218d0
Author: Sebastian Keller <skeller gnome org>
Date:   Thu Jan 30 09:54:02 2020 +0100

    display: Unref selection on shutdown
    
    Otherwise it will be leaked and the dispose method added in the previous
    commit would never be run.
    
    Fixes parts of https://gitlab.gnome.org/GNOME/mutter/issues/1006
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/1001

 src/core/display.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/core/display.c b/src/core/display.c
index 8a6d69440..80a325125 100644
--- a/src/core/display.c
+++ b/src/core/display.c
@@ -1022,6 +1022,7 @@ meta_display_close (MetaDisplay *display,
   g_clear_object (&display->sound_player);
 
   meta_clipboard_manager_shutdown (display);
+  g_clear_object (&display->selection);
 
   g_object_unref (display);
   the_display = NULL;