KVO exception under WebAVPictureInPictureController stopPictureInPicture
Pull request: https://github.com/WebKit/WebKit/pull/4142
<rdar://problem/99618553>
Committed 254288@main (32c0971e6d80): <https://commits.webkit.org/254288@main> Reviewed commits have been landed. Closing PR #4142 and removing active labels.