https://bugs.webkit.org/show_bug.cgi?id=125042

Reviewed by Mario Sanchez Prada.

Source/WebCore:

When an AX text marker that references a node in a detached document is used to create a text marker range, a crash occurs
because the method to determine commonTreeScopes does not account for when there are no common tree scopes.

Test: platform/mac/accessibility/ordered-textmarker-crash.html

* accessibility/AccessibilityObject.cpp:
(WebCore::AccessibilityObject::visiblePositionRangeForUnorderedPositions):
* dom/TreeScope.cpp:
(WebCore::commonTreeScope):

LayoutTests:

* platform/mac/accessibility/ordered-textmarker-crash-expected.txt: Added.
* platform/mac/accessibility/ordered-textmarker-crash.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@159932 268f45cc-cd09-0410-ab3c-d52691b4dbfc