Null check

Bug: 1131380
Change-Id: I04477396fa11afb24a89c1447e799880c857b512
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2426248
Auto-Submit: Aaron Leventhal <aleventhal@chromium.org>
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809883}

third_party/blink/renderer/modules/accessibility/ax_object.cc

@@ -1868,7 +1868,7 @@ bool AXObject::IsARIAControlledByTextboxWithActiveDescendant() const {
     return false;
 
   const AXObject* focused_object = AXObjectCache().GetOrCreate(focused_element);
-  if (!focused_object->IsTextControl())
+  if (!focused_object || !focused_object->IsTextControl())
     return false;
 
   if (!focused_object->GetAOMPropertyOrARIAAttribute(