Fix crash on Linux when a normal window is created after a hidden window.

chrome/browser/ui/gtk/apps/native_app_window_gtk.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/gtk/apps/native_app_window_gtk.h"
 
 #include <gdk/gdkx.h>
 #include <vector>
 
 #include "base/message_loop/message_pump_gtk.h"
@@ skipping 294 matching lines @@
                                              GdkEvent* gdk_event) {
   // Work around GTK+ not reporting minimization state changes. Listen
   // for _NET_WM_STATE property changes and use _NET_WM_STATE_HIDDEN's
   // presence to set or clear the iconified bit if _NET_WM_STATE_HIDDEN
   // is supported. http://crbug.com/162794.
   XEvent* x_event = static_cast<XEvent*>(gdk_x_event);
   std::vector< ::Atom> atom_list;
 
   if (x_event->type == PropertyNotify &&
       x_event->xproperty.atom == atom_cache_.GetAtom("_NET_WM_STATE") &&
+      GTK_WIDGET(window_)->window &&
       ui::GetAtomArrayProperty(GDK_WINDOW_XWINDOW(GTK_WIDGET(window_)->window),
                                "_NET_WM_STATE",
                                &atom_list)) {
     std::vector< ::Atom>::iterator it =
         std::find(atom_list.begin(),
                   atom_list.end(),
                   atom_cache_.GetAtom("_NET_WM_STATE_HIDDEN"));
     state_ = (it != atom_list.end()) ? GDK_WINDOW_STATE_ICONIFIED :
         static_cast<GdkWindowState>(state_ & ~GDK_WINDOW_STATE_ICONIFIED);
 
@@ skipping 378 matching lines @@
     hints_mask |= GDK_HINT_MAX_SIZE;
   }
   if (hints_mask) {
     gtk_window_set_geometry_hints(
         window_,
         GTK_WIDGET(window_),
         &hints,
         static_cast<GdkWindowHints>(hints_mask));
   }
 }