[mutter] core: Free clipboard selection source on shutdown

[Carlos Garnacho <carlosg src gnome org>]

commit 019643bad081f7a29119a99ca5ecbc5c2ba3ee56
Author: Sebastian Keller <skeller gnome org>
Date:   Fri Jun 5 19:38:23 2020 +0200

    core: Free clipboard selection source on shutdown
    
    The clipboard manager is the only code to ever set the display selection
    source, so it should also be responsible for unsetting it when the
    clipboard manager gets shut down.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1293

 src/core/meta-clipboard-manager.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/core/meta-clipboard-manager.c b/src/core/meta-clipboard-manager.c
index 69b00d85a8..794195f41a 100644
--- a/src/core/meta-clipboard-manager.c
+++ b/src/core/meta-clipboard-manager.c
@@ -171,6 +171,7 @@ meta_clipboard_manager_shutdown (MetaDisplay *display)
 {
   MetaSelection *selection;
 
+  g_clear_object (&display->selection_source);
   g_clear_pointer (&display->saved_clipboard, g_bytes_unref);
   g_clear_pointer (&display->saved_clipboard_mimetype, g_free);
   selection = meta_display_get_selection (display);