Crash when restoring a QDockAreaLayout

QMainWindow::restoreState crashes when a QDockWidget is restored on a screen that moved.

Repro:

• Move a QDockWidget outside the QMainWindow, on a secondary screen
• Save the layout and exit
• Move the secondardy screen (for instance, if it was on the right, move it on the top). Or change your main monitor from 4K to FullHD (happens a lot to me)
• Restore
• -> crash

See attachement for standalone repro.

The callstack is:

> Qt6Widgetsd.dll!QDockAreaLayout::constrainedRect(QRect rect, QWidget * widget) Ligne 3032 C++
Qt6Widgetsd.dll!QDockAreaLayoutInfo::restoreState(QDataStream & stream, QList<QDockWidget *> & widgets, bool testing) Ligne 1941 C++
Qt6Widgetsd.dll!QDockAreaLayout::restoreState(QDataStream & stream, const QList<QDockWidget *> & _dockwidgets, bool testing) Ligne 2346 C++
Qt6Widgetsd.dll!QMainWindowLayoutState::restoreState(QDataStream & _stream, const QMainWindowLayoutState & oldState) Ligne 1188 C++
Qt6Widgetsd.dll!QMainWindowLayout::restoreState(QDataStream & stream) Ligne 2773 C++
Qt6Widgetsd.dll!QMainWindow::restoreState(const QByteArray & state, int version) Ligne 1291 C++
displaysetup.exe!main(int argc, char * * argv) Ligne 68 C++

At that point screen is nullptr because QGuiApplication::screenAt() returned nullptr.

Of course my suggested fix is to replace

QScreen *screen;
if (QGuiApplication::primaryScreen()->virtualSiblings().size() > 1)
     screen = QGuiApplication::screenAt(rect.topLeft());
else
     screen = widget->screen();

by

QScreen *screen = nullptr;
if (QGuiApplication::primaryScreen()->virtualSiblings().size() > 1)
     screen = QGuiApplication::screenAt(rect.topLeft());
if(screen == nullptr)
     screen = widget->screen();