[mutter] backend: Destroy backend explicitly

[Marge Bot <marge-bot src gnome org>]

commit c5f699b8b3b668b2a090201012745ac1fad39be4
Author: Jonas Ådahl <jadahl gmail com>
Date:   Fri Mar 12 08:39:53 2021 +0100

    backend: Destroy backend explicitly
    
    This now ensures that calling meta_release_backend() destroys the
    backend.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1775>

 src/backends/meta-backend.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)
---
diff --git a/src/backends/meta-backend.c b/src/backends/meta-backend.c
index 0a8fb872e5..aa256f56a5 100644
--- a/src/backends/meta-backend.c
+++ b/src/backends/meta-backend.c
@@ -252,6 +252,13 @@ meta_backend_dispose (GObject *object)
   G_OBJECT_CLASS (meta_backend_parent_class)->dispose (object);
 }
 
+static void
+meta_backend_destroy (MetaBackend *backend)
+{
+  g_object_run_dispose (G_OBJECT (backend));
+  g_object_unref (backend);
+}
+
 static void
 meta_backend_sync_screen_size (MetaBackend *backend)
 {
@@ -1534,7 +1541,7 @@ meta_init_backend (GType         backend_gtype,
 void
 meta_release_backend (void)
 {
-  g_clear_object (&_backend);
+  g_clear_pointer (&_backend, meta_backend_destroy);
 }
 
 void