Reviewed by Richard

    Reviewed by Richard

        Fix for this bug:

        <rdar://problem/3857775> 8A293: Mail.app crashes converting copy-pasted text into plain text

        * khtml/xml/dom2_rangeimpl.cpp:
        (DOM::RangeImpl::commonAncestorContainer): Return the document element if no common ancestor container
        was found. This can happen in cases where the DOM was built from malformed markup (as in the case
        of this bug where there is content after the body tag). Did a little code clean up as well.
        (DOM::RangeImpl::compareBoundaryPoints): Made code more robust by adding some null checks.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@8103 268f45cc-cd09-0410-ab3c-d52691b4dbfc