Check for NULL NativeView in linux/mac Screen::GetDisplayNearestWindow().

ui/gfx/screen_mac.mm

 // Copyright (c) 2012 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 "ui/gfx/screen.h"
 
 #import <ApplicationServices/ApplicationServices.h>
 #import <Cocoa/Cocoa.h>
 
 #include <map>
@@ skipping 109 matching lines @@
   }
 
   virtual std::vector<gfx::Display> GetAllDisplays() const OVERRIDE {
     return displays_;
   }
 
   virtual gfx::Display GetDisplayNearestWindow(
       gfx::NativeView view) const OVERRIDE {
     NSWindow* window = nil;
 #if !defined(USE_AURA)
-    window = [view window];
+    if (view)
+      window = [view window];
 #endif
     if (!window)
       return GetPrimaryDisplay();
     NSScreen* match_screen = [window screen];
     if (!match_screen)
       return GetPrimaryDisplay();
     return GetDisplayForScreen(match_screen);
   }
 
   virtual gfx::Display GetDisplayNearestPoint(
@@ skipping 133 matching lines @@
 
 namespace gfx {
 
 #if !defined(USE_AURA)
 Screen* CreateNativeScreen() {
   return new ScreenMac;
 }
 #endif
 
 }