[Reg 6.6 -> 6.7] qmlsc: type mismatch generates uncompilable code

A type mismatch in two C++ defined components that are wired by QML (here moo/int vs foo/unsigned short)

    property Moo moo

    QtObject {
        readonly property Foo foo: Foo {
            uid: root.moo?.uid ?? 0xFFFF  // Fails
            //uid: root.moo.uid  // Works
        }
    }

leads to:

/appfoo_Main_qml.cpp:315:8: error: inconsistent types ‘short unsigned int’ and ‘unsigned int’ deduced for lambda return type
  315 | return uint(r2_3.toInteger());
      |        ^~~~~~~~~~~~~~~~~~~~~~

While this is clearly a problem of inconsistent interfaces on the C++ side, I'd expect some kind of warning/error before becoming qml.cpp file.

On the other side, it's inconsistent between the two commented works/fails lines. And it's a regression for 6.6, as both variants work there.