[gtk/mcatanzaro/#1349] wayland: Fix a very-frequent crasher

[Michael Catanzaro <mcatanzaro src gnome org>]

commit b9ccd39e24a49e180d38f678a63af4d9548dac4d
Author: Michael Catanzaro <mcatanzaro igalia com>
Date:   Fri Sep 21 20:37:17 2018 -0500

    wayland: Fix a very-frequent crasher
    
    This is probably a bandaid rather than a real fix. For some reason,
    impl->display_server.wl_surface is NULL here, and we crash in that
    case, so let's not do that. Requires further investigation.
    
    Fixes #1349

 gdk/wayland/gdkwindow-wayland.c | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/gdk/wayland/gdkwindow-wayland.c b/gdk/wayland/gdkwindow-wayland.c
index 5f162770a0..58bd2744aa 100644
--- a/gdk/wayland/gdkwindow-wayland.c
+++ b/gdk/wayland/gdkwindow-wayland.c
@@ -766,6 +766,10 @@ gdk_wayland_window_attach_image (GdkWindow *window)
 
   g_assert (_gdk_wayland_is_shm_surface (impl->staging_cairo_surface));
 
+  /* XXX: Is this correct? */
+  if (!impl->display_server.wl_surface)
+    return;
+
   /* Attach this new buffer to the surface */
   wl_surface_attach (impl->display_server.wl_surface,
                      _gdk_wayland_shm_surface_get_wl_buffer (impl->staging_cairo_surface),