QtDeclarative 6.10 crash fix

[Akseli Lahtinen]

Hello

There is a crash in QtDeclarative code that can happen with various things, such
as systemtray applets changing their state, most notable example being PowerDevil.

Cherrypicking this patch should fix that crash issue:
https://codereview.qt-project.org/c/qt/qtdeclarative/+/696524

More information about the crash:
https://bugs.kde.org/show_bug.cgi?id=512754


Best regards,
- Akseli