[mutter] wayland/surface: Check for surface role in meta_wayland_surface_get_window()

[Jonas Ådahl <jadahl src gnome org>]

commit dbe919ef922368d952ff3f21db411d0160d4c42b
Author: Robert Mader <robert mader posteo de>
Date:   Mon Mar 30 15:53:29 2020 +0200

    wayland/surface: Check for surface role in meta_wayland_surface_get_window()
    
    The function can get called without valid surface role, e.g. from
    `zwp_xwayland_keyboard_grab_manager_grab()`.
    
    Debugged by @piegamesde
    
    Fixes https://gitlab.gnome.org/GNOME/mutter/-/issues/1147

 src/wayland/meta-wayland-surface.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/src/wayland/meta-wayland-surface.c b/src/wayland/meta-wayland-surface.c
index f7cdb0171..7e5e8eb71 100644
--- a/src/wayland/meta-wayland-surface.c
+++ b/src/wayland/meta-wayland-surface.c
@@ -1745,6 +1745,9 @@ meta_wayland_surface_role_get_window (MetaWaylandSurfaceRole *surface_role)
 MetaWindow *
 meta_wayland_surface_get_window (MetaWaylandSurface *surface)
 {
+  if (!surface->role)
+    return NULL;
+
   return meta_wayland_surface_role_get_window (surface->role);
 }