ListView sections don't work with a dot syntax (e.g. "gadget.size") if using Q_GADGETs

Steps to reproduce:

• Run the attached reproducer.

What done in the reproducer:

• Create a ListView (gadgetListView in the reproducer) in QML, which accesses QAbstractListModel defined in C++ (myGadgetList in the reproducer). 
• Each entry of the QAbstractListModel is an instance of a class defined with Q_GADGET macro (MyGadget class in the reproducer).
• Let the ListView to classify entries into sections automatically, depending on each entry's property (gadget.size), as follows:

        section

{             property: "gadget.size"             criteria: ViewSection.FullString             delegate: sectionHeading         }

• This section property (dot notation access : "gadget.size") does not work. The entries in myGadgetList are not classified in sections in the ListView.
• The same approach works for myObjectList, a list of instances with Q_OBJECT macro.

Side note:

• The user is pointing out that this might be being caused by QQmlDelegateModelPrivate::variantValue(), where it seems assuming only Q_OBJECT, i.e. casting the entry to QObject pointer.

• Besides ListView Sections, Qt 6.7.0 shows a bit different behvior than 6.6.x.
    The notation "object.size" and "gadget.name" work with 6.6.x, but not with 6.7.0, while "object.name" and "gadget.name" work with 6.0.x and 6.7.0 both.
    (See attached qt_6_6_2.png, qt_6_6_3.png and qt_6_7_0.png)