Add more checks to prevent crashes when accessing name/opener properties

Source/core/loader/FrameLoader.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008 Alp Toker <alp@atoker.com>
  * Copyright (C) Research In Motion Limited 2009. All rights reserved.
  * Copyright (C) 2011 Kris Jordan <krisjordan@gmail.com>
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ skipping 526 matching lines @@
 }
 
 void FrameLoader::scheduleCheckCompleted()
 {
     m_shouldCallCheckCompleted = true;
     startCheckCompleteTimer();
 }
 
 LocalFrame* FrameLoader::opener()
 {
-    ASSERT(m_client);
     // FIXME: Temporary hack to stage converting locations that really should be Frame.
-    return toLocalFrame(m_client->opener());
+    return m_client ? toLocalFrame(m_client->opener()) : 0;
 }
 
 void FrameLoader::setOpener(LocalFrame* opener)
 {
-    ASSERT(m_client);
-    m_client->setOpener(opener);
+    // If the frame is already detached, the opener has already been cleared.
+    if (m_client)
+        m_client->setOpener(opener);
 }
 
 bool FrameLoader::allowPlugins(ReasonForCallingAllowPlugins reason)
 {
     Settings* settings = m_frame->settings();
     bool allowed = m_client->allowPlugins(settings && settings->pluginsEnabled());
     if (!allowed && reason == AboutToInstantiatePlugin)
         m_client->didNotAllowPlugins();
     return allowed;
 }
@@ skipping 903 matching lines @@
 {
     SandboxFlags flags = m_forcedSandboxFlags;
     if (LocalFrame* parentFrame = m_frame->tree().parent())
         flags |= parentFrame->document()->sandboxFlags();
     if (HTMLFrameOwnerElement* ownerElement = m_frame->ownerElement())
         flags |= ownerElement->sandboxFlags();
     return flags;
 }
 
 } // namespace WebCore