REGRESSION (r159208): Crash when clicking scrubber after navigating away/back to video
https://bugs.webkit.org/show_bug.cgi?id=137715

Reviewed by Darin Adler.

Simple null-check of m_player in refreshCachedTime.

* html/HTMLMediaElement.cpp:
(WebCore::HTMLMediaElement::refreshCachedTime):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@174720 268f45cc-cd09-0410-ab3c-d52691b4dbfc