<rdar://problem/9328684> and https://bugs.webkit.org/show_bug.cgi?id=62764 Frequent...

<rdar://problem/9328684> and https://bugs.webkit.org/show_bug.cgi?id=62764 Frequent crashes due to null frame below ApplicationCacheHost::scheduleLoadFallbackResourceFromApplicationCache

Reviewed by Sam Weinig.

No way to reproduce without special malloc debugging and that doesn't even reproduce on all platforms.  So still no test.

* loader/DocumentLoader.cpp:
(WebCore::DocumentLoader::detachFromFrame): Protect m_frame for the duration of this method.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@105556 268f45cc-cd09-0410-ab3c-d52691b4dbfc