libweston-desktop/xdg-shell-v6: Fix crash when surface has buffer at creation

When a surface has a buffer at creation time we send an error, which results
in a disconnection and all resources being destroyed.

Since we send that error and return before performing the configure_list init
weston_desktop_xdg_surface_destroy() will walk an uninitialized list and
dereference a NULL pointer.

Initializing the list earlier prevents this from happening.

Signed-off-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>

libweston-desktop/xdg-shell-v6.c

@@ -1370,6 +1370,7 @@ weston_desktop_xdg_shell_protocol_get_xdg_surface(struct wl_client *wl_client,
 
 	surface->desktop = weston_desktop_client_get_desktop(client);
 	surface->surface = wsurface;
+	wl_list_init(&surface->configure_list);
 
 	surface->desktop_surface =
 		weston_desktop_surface_create(surface->desktop, client,
@@ -1395,8 +1396,6 @@ weston_desktop_xdg_shell_protocol_get_xdg_surface(struct wl_client *wl_client,
 				       "xdg_surface must not have a buffer at creation");
 		return;
 	}
-
-	wl_list_init(&surface->configure_list);
 }
 
 static void