Allow using const pointers as parameters of C++ functions called by QML

I have an invokable function in C++ that should be const with const parameters:

Q_INVOKABLE QPoint findClosestAvailableTilePos(const QPoint &tilePos, const SceneItemComponent *sceneItemComponent = nullptr) const;

I register it with QML like this:

qmlRegisterUncreatableType<SceneItemComponent>("Isle", 1, 0, "SceneItemComponent", "SceneItemComponent should not be created in QML");

If I try to call this with a SceneItemComponent object in JavaScript, the parameter simply becomes null in C++. Changing the parameter to a non-const SceneItemComponent* is a workaround, but not that nice, because it means that everywhere I use this function in C++ has to be adapted (and sometimes const_casted).

It would be better if it were possible to use the const type in QML and just get an error if any non-const operations (getters, setters, invokables) were performed on it, if that's even possible. I don't know if e.g. moc even stores constness of functions, or whether such a change to the QML engine would affect performance adversely... but it would be nice to have.