Event handler IDL attribute setter works in browsers without an active document #12014
Description
Tests here web-platform-tests/wpt#56715
Interestingly, browsers don't match the spec for event handler IDL attribute setters. element.onclick = () => ran = true; creates an event handler even though the https://html.spec.whatwg.org/#determining-the-target-of-an-event-handler returns null per spec.
Originally posted by @zcorpan in #11441 (comment)