added prevent check for m_player in duration()

Source/core/html/HTMLMediaElement.cpp

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 2063 matching lines @@
 {
     if (m_mediaController) {
         exceptionState.throwDOMException(InvalidStateError, "The element is slaved to a MediaController.");
         return;
     }
     seek(time, exceptionState);
 }
 
 double HTMLMediaElement::duration() const
 {
-    if (m_readyState < HAVE_METADATA)
+    // FIXME: remove m_player check once we figure out how m_player is going
+    // out of sync with readystate. m_player is cleared but readystate is not set
+    // to HAVE_NOTHING
+    if (!m_player || m_readyState < HAVE_METADATA)
         return std::numeric_limits<double>::quiet_NaN();
 
     // FIXME: Refactor so m_duration is kept current (in both MSE and
     // non-MSE cases) once we have transitioned from HAVE_NOTHING ->
     // HAVE_METADATA. Currently, m_duration may be out of date for at least MSE
     // case because MediaSource and SourceBuffer do not notify the element
     // directly upon duration changes caused by endOfStream, remove, or append
     // operations; rather the notification is triggered by the WebMediaPlayer
     // implementation observing that the underlying engine has updated duration
     // and notifying the element to consult its MediaSource for current
@@ skipping 1879 matching lines @@
 
 #if ENABLE(WEB_AUDIO)
 void HTMLMediaElement::clearWeakMembers(Visitor* visitor)
 {
     if (!visitor->isAlive(m_audioSourceNode) && audioSourceProvider())
         audioSourceProvider()->setClient(0);
 }
 #endif
 
 }