Fix crash on launch of WebKit processes, if the process launcher is deleted early.
<rdar://problem/119993070>
Pull request: https://github.com/WebKit/WebKit/pull/22425
Committed 272686@main (9419ea9f50b8): <https://commits.webkit.org/272686@main> Reviewed commits have been landed. Closing PR #22425 and removing active labels.