Fixes possible crash if the window hosting a menu was closed while the

views/widget/widget_gtk.cc

Index: views/widget/widget_gtk.cc
diff --git a/views/widget/widget_gtk.cc b/views/widget/widget_gtk.cc
index d850b90ee327a50328573772f0183a9fe89491a7..006a089e80d4fd39a0df172ee0fec44d7660779f 100644
--- a/views/widget/widget_gtk.cc
+++ b/views/widget/widget_gtk.cc
@@ -989,6 +989,9 @@ gboolean WidgetGtk::OnGrabBrokeEvent(GtkWidget* widget, GdkEvent* event) {
 }
 
 void WidgetGtk::OnGrabNotify(GtkWidget* widget, gboolean was_grabbed) {
+  if (!window_contents_)
+    return;  // Grab broke after window destroyed, don't try processing it.
+
   gtk_grab_remove(window_contents_);
   HandleGrabBroke();
 }