Bug 1768269: Use IgnoredErrorResult instead of ErrorResult in LocalAccessible::IsActiveDescendant. r=eeejay

QuerySelector can fail if the id is invalid; e.g. if it contains a quote (") character.
ErrorResult treats a failure as an exception, so it asserts.
We explicitly check for and handle failure ourselves, so use IgnoredErrorResult instead.

Differential Revision: https://phabricator.services.mozilla.com/D151564

accessible/generic/LocalAccessible.cpp

@@ -2966,7 +2966,7 @@ bool LocalAccessible::IsActiveDescendant(LocalAccessible** aWidget) const {
   selector.AppendPrintf(
       "[aria-activedescendant=\"%s\"]",
       NS_ConvertUTF16toUTF8(mContent->GetID()->GetUTF16String()).get());
-  ErrorResult er;
+  IgnoredErrorResult er;
 
   dom::Element* widgetElm =
       docOrShadowRoot->AsNode().QuerySelector(selector, er);