[Windows] Unreviewed test correction:  Prevent DumpRenderTree crashes
* DumpRenderTree/win/AccessibilityUIElementWin.cpp:
(AccessibilityUIElement::role): Prevent crashes when m_element is null. This
happends in some of the 'accessibility' test cases.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@151361 268f45cc-cd09-0410-ab3c-d52691b4dbfc