unset std::optional may be dereferenced in currentUserInterfaceIdiom().
<rdar://110626776>
Pull request: https://github.com/WebKit/WebKit/pull/14870
Committed 265076@main (9b3f38967bcd): <https://commits.webkit.org/265076@main> Reviewed commits have been landed. Closing PR #14870 and removing active labels.