Otherwise we'll have a cursor sprite backed by a surface that no longer
exist. This usually doesn't happen, but can happen in rare situations
related to pointer capability changes Wayland client cursor changes and
hotplugs.
Fixes the following crash:
#0 meta_wayland_buffer_get_resource() at ../src/wayland/meta-wayland-buffer.c:128
#1 realize_cursor_sprite_from_wl_buffer_for_gpu() at ../src/backends/native/meta-cursor-renderer-native.c:1649
#2 realize_cursor_sprite_for_gpu() at ../src/backends/native/meta-cursor-renderer-native.c:1869
#3 realize_cursor_sprite() at ../src/backends/native/meta-cursor-renderer-native.c:1887
#4 meta_cursor_renderer_native_update_cursor() at ../src/backends/native/meta-cursor-renderer-native.c:1100
#5 meta_cursor_renderer_update_cursor() at ../src/backends/meta-cursor-renderer.c:414
#6 meta_cursor_renderer_force_update() at ../src/backends/meta-cursor-renderer.c:449
#7 update_cursors() at ../src/backends/meta-backend.c:328
#8 meta_backend_monitors_changed() at ../src/backends/meta-backend.c:338
#9 meta_monitor_manager_notify_monitors_changed() at ../src/backends/meta-monitor-manager.c:3590
#10 meta_monitor_manager_rebuild() at ../src/backends/meta-monitor-manager.c:3678
#11 meta_monitor_manager_native_apply_monitors_config() at ../src/backends/native/meta-monitor-manager-native.c:343
#12 meta_monitor_manager_apply_monitors_config() at ../src/backends/meta-monitor-manager.c:706
#13 meta_monitor_manager_ensure_configured() at ../src/backends/meta-monitor-manager.c:779
#14 meta_monitor_manager_reconfigure() at ../src/backends/meta-monitor-manager.c:3738
#15 meta_monitor_manager_reload() at ../src/backends/meta-monitor-manager.c:3745
or the following on gnome-43:
#0 meta_wayland_surface_get_buffer at ../src/wayland/meta-wayland-surface.c:441
#1 meta_cursor_sprite_wayland_get_buffer at ../src/wayland/meta-cursor-sprite-wayland.c:83
#2 realize_cursor_sprite_from_wl_buffer_for_gpu at ../src/backends/native/meta-cursor-renderer-native.c:1612
#3 realize_cursor_sprite_for_gpu at ../src/backends/native/meta-cursor-renderer-native.c:1836
#4 realize_cursor_sprite at ../src/backends/native/meta-cursor-renderer-native.c:1854
#5 meta_cursor_renderer_native_update_cursor at ../src/backends/native/meta-cursor-renderer-native.c:1087
#6 meta_cursor_renderer_update_cursor at ../src/backends/meta-cursor-renderer.c:413
#7 meta_cursor_renderer_force_update at ../src/backends/meta-cursor-renderer.c:448
#8 update_cursors at ../src/backends/meta-backend.c:344
#9 meta_backend_monitors_changed at ../src/backends/meta-backend.c:354
Related: https://bugzilla.redhat.com/show_bug.cgi?id=2185113
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2968>
