rdar://122451549 The changes to move AXSelectedTextMarkerRange off of the main thread resulted in an issue where unconnected nodes (for example, the static text of an <input type=text>) were not having their values updated with the input field. This means that when the selected text range of that input is queried, and it references the unconnected node, we return a null string since it is not up-to-date.
*** This bug has been marked as a duplicate of bug 270499 ***