Fix crash by adding check for weak linked symbol PLQueryRegistered.
<rdar://99000302>
Pull request: https://github.com/WebKit/WebKit/pull/3720
Committed 253910@main (4eb24af4acc9): <https://commits.webkit.org/253910@main> Reviewed commits have been landed. Closing PR #3720 and removing active labels.
Re-opened since this is blocked by bug 244507