Qt Quick: Crash when deleting dockWidget in MDI

[MiKom]

Environment

• Qt 6.6.2
• Windows 11
• Visual Studio 2022 compiler 19.38.33135 amd64

Steps to reproduce

1. Add the following code to examples\qtquick\mdi\main.cpp:

   QTimer::singleShot(std::chrono::seconds(3), [&]{
       delete dw1;
       delete dw2;
   });

2. Run the qtquick_mdi.exe example
3. Wait

Expected result

dw1 and dw2 are properly deleted and disappear taking their children with them.

Actual result

Application crashes with the following stacktrace: https://gist.github.com/MiKom/e9fe77c45004a2139a8410ba0c90740e

[iamsergio]

Fixed in 18663268bb521733cac6df6418809f179cbe0a01