bindings: Add empty checks for toV8()

Source/web/WebPluginContainerImpl.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2014 Opera Software ASA. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 445 matching lines @@
         return v8::Local<v8::Object>();
 
     if (!frame->script().canExecuteScripts(NotAboutToExecuteScript))
         return v8::Local<v8::Object>();
 
     ScriptState* scriptState = ScriptState::forMainWorld(frame);
     if (!scriptState->contextIsValid())
         return v8::Local<v8::Object>();
 
     v8::Local<v8::Value> v8value = toV8(m_element.get(), scriptState->context()->Global(), scriptState->isolate());
+    if (v8value.IsEmpty())
+        return v8::Local<v8::Object>();
     ASSERT(v8value->IsObject());
 
     return v8::Local<v8::Object>::Cast(v8value);
 }
 
 WebString WebPluginContainerImpl::executeScriptURL(const WebURL& url, bool popupsAllowed)
 {
     LocalFrame* frame = m_element->document().frame();
     if (!frame)
         return WebString();
@@ skipping 538 matching lines @@
     for (size_t i = 0; i < cutOutRects.size(); i++)
         cutOutRects[i].move(-frameRect().x(), -frameRect().y());
 }
 
 bool WebPluginContainerImpl::pluginShouldPersist() const
 {
     return m_webPlugin->shouldPersist();
 }
 
 } // namespace blink