[mutter] cursor-tracker/x11: Don't leak xfixes cursor sprite

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 5f5ef704fc2733e4aaa38a51c2e864d3cb83b708
Author: Jonas Ådahl <jadahl gmail com>
Date:   Fri Jul 31 21:09:14 2020 +0200

    cursor-tracker/x11: Don't leak xfixes cursor sprite
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1391

 src/backends/x11/meta-cursor-tracker-x11.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/backends/x11/meta-cursor-tracker-x11.c b/src/backends/x11/meta-cursor-tracker-x11.c
index 6f718f9e89..24e303fe31 100644
--- a/src/backends/x11/meta-cursor-tracker-x11.c
+++ b/src/backends/x11/meta-cursor-tracker-x11.c
@@ -143,6 +143,7 @@ meta_cursor_tracker_x11_dispose (GObject *object)
   MetaCursorTrackerX11 *tracker_x11 = META_CURSOR_TRACKER_X11 (object);
 
   g_clear_handle_id (&tracker_x11->update_position_timeout_id, g_source_remove);
+  g_clear_object (&tracker_x11->xfixes_cursor);
 
   G_OBJECT_CLASS (meta_cursor_tracker_x11_parent_class)->dispose (object);
 }