Empty QML type registration prevents plugin from loading

Running the attached example leads to the error "Cannot protect module Charts 1 as it was never registered". The plugin doesn't register any QML types implemented in C++, but only includes a QML component (RedRect.qml - compiled in as a resource). A workaround is to register a dummy type (in import/chartsplugin.cpp uncomment line 16).

Is this a problem in Qt or is there a proper solution for this in the application code? I am looking for a solution that would work for both, Qt5.15 and Qt5.12 (and hence it's not adding "qmltypes" to CONFIG).