[mutter] window: Get backend from context when updating monitors

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

commit cf848c577efca8039bfc8aabb98cb0c5b0b28eca
Author: Jonas Ådahl <jadahl gmail com>
Date:   Wed Aug 3 22:58:11 2022 +0200

    window: Get backend from context when updating monitors
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2554>

 src/core/window.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/src/core/window.c b/src/core/window.c
index ee5ba67de2..621abd9a59 100644
--- a/src/core/window.c
+++ b/src/core/window.c
@@ -3652,7 +3652,8 @@ find_monitor_by_winsys_id (MetaWindow *window,
 void
 meta_window_update_for_monitors_changed (MetaWindow *window)
 {
-  MetaBackend *backend = meta_get_backend ();
+  MetaContext *context = meta_display_get_context (window->display);
+  MetaBackend *backend = meta_context_get_backend (context);
   MetaMonitorManager *monitor_manager =
     meta_backend_get_monitor_manager (backend);
   const MetaLogicalMonitor *old, *new;