[Reg 6.6 -> 6.7] Bluetooth QML examples start crashing after recent additions to QtDeclarative

I first noticed it while doing a UI update for Bluetooth HeartRate Game, but I can also reproduce a similar crash with Bluetooth Low Energy Scanner example.

I use an ASAN build of Qt.

Steps to reproduce:

• Build HeartRate Game example from the dev branch.
• Run it with the --simulator command line argument, so that it would not require an actual bluetooth device to connect to.
• Press "START SEARCH" for the first time - it will simulate the search and show a bunch of "Demo device" entries.
• Staying on the same page, press "START SEARCH" again -> the application will trigger an ASAN "heap-use-after-free" error and crash.

The full ASAN log is attached.

I suspect that it is caused by https://codereview.qt-project.org/c/qt/qtdeclarative/+/520292 because it's where the ASAN log points to.