[REG 5.15.3 -> 5.15.4] Service worker related renderer crash after upgrade

• Visit twitch.tv with QtWebEngine 5.15.3 simplebrowser, and make sure it installs its service worker (maybe wait a bit or double-check in devtools)
• Visit twitch.tv with QtWebEngine 5.15.4 (and the same data)
• Get a segfault in "ServiceWorker thread"

Strangely enough, I can't reproduce with a developer build (so I was unable to get a stacktrace so far), but I suspect this is just QTBUG-72532 again.

As an aside, with 5.15.3 (and .4), I'm still getting various user reports related to QTBUG-82105 (a full application crash due to a corrupt service worker cache), probably after the application was closed in an unclean way, causing the corruption. Since I've never seen this happen in Chrome, I still wonder whether there's some code in Chrome validating the cache and discarding it when it is invalid in some way, which is missing in QtWebEngine...