Reviewed by Geoff.

        Fix for <rdar://problem/4948128> REGRESSION: A crash occurs at 
        WebCore::Frame::view() after completing a query at mapquest.com 
        then switching to Bookmarks view

        This is just a null-check. If you are in strict mode and ask for 
        the clientWidth or clientHeight after the document was removed from 
        it's parent, we no longer have a frameView, so we have to null-
        check it. I added null checks for the FrameView in some other 
        places where it seems like we could potentially run into this 
        issue.

LayoutTests:
        Reviewed by Geoff.

        Test for <rdar://problem/4948128> REGRESSION: A crash occurs at 
        WebCore::Frame::view() after completing a query at mapquest.com 
        then switching to Bookmarks view

        * fast/dom/clientWidthAfterDocumentIsRemoved-expected.checksum: Added.
        * fast/dom/clientWidthAfterDocumentIsRemoved-expected.png: Added.
        * fast/dom/clientWidthAfterDocumentIsRemoved-expected.txt: Added.
        * fast/dom/clientWidthAfterDocumentIsRemoved.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@19100 268f45cc-cd09-0410-ab3c-d52691b4dbfc