[mutter] core/window: Don't set a preferred output when there is none

[Jonas Ådahl <jadahl src gnome org>]

commit 7562eb600659e86304d90f3fe666116a081c75ea
Author: Jonas Ådahl <jadahl gmail com>
Date:   Wed Apr 12 14:21:49 2017 +0800

    core/window: Don't set a preferred output when there is none
    
    If there are no active logical monitors, don't try to dereference a
    NULL one to get a preferred output winsys id. Instead just set an
    invalid one.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=730551

 src/core/window.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/src/core/window.c b/src/core/window.c
index ec3083f..f3ff8fd 100644
--- a/src/core/window.c
+++ b/src/core/window.c
@@ -1039,7 +1039,10 @@ _meta_window_shared_new (MetaDisplay         *display,
   window->compositor_private = NULL;
 
   window->monitor = meta_window_calculate_main_logical_monitor (window);
-  window->preferred_output_winsys_id = window->monitor->winsys_id;
+  if (window->monitor)
+    window->preferred_output_winsys_id = window->monitor->winsys_id;
+  else
+    window->preferred_output_winsys_id = UINT_MAX;
 
   window->tile_match = NULL;