DOMApplicationCache::scriptExecutionContext() isn't prepared have its frame destroyed. <rdar://problem/7545104>
Created attachment 46852 [details] proposed fix
Comment on attachment 46852 [details] proposed fix r=me I think you need a follow-up patch to fix callers of scriptExecutionContext() so they all check for null, though.
Committed <http://trac.webkit.org/changeset/53433>.