[REG Qt 6.3.2 -> 6.4.0] Default button is not triggered when widget in a sub-layout has focus

When a widget in a sub-layout has focus, pressing Enter does not trigger the dialog's default button.

Steps to reproduce:

1. Run the attached example project
2. Set focus on LineEdit1 and press Enter
   Observed behavior: The default button is not triggered and the dialog does not close
3. Set focus on LineEdit2 and press Enter
   Observed behavior: The default button is triggered and the dialog closes

Furthermore, when the following environment variables are unset:

• GNOME_DESKTOP_SESSION_ID=this-is-deprecated
  XDG_CURRENT_DESKTOP=GNOME-Flashback:GNOME

then behavior is as expected i.e. pressing Enter closes the dialog regardless of which LineEdit has focus.