qt: color scheme is not applied correctly

changing the style fails

something is wrong with the ColorSchemeModel::ColorScheme enum registration

[0000557059920fd0] [qt] qt generic warning: qml message qrc:/style/VLCStyle.qml:44 Unable to assign int to [unknown property type]
[0000557059920fd0] [qt] qt generic warning: qml message qrc:/style/VLCStyle.qml:38 Unable to assign int to [unknown property type]

if I register explicitly the enum, the code is working again, theoretically we shouldn't have to register this enum as ColorSchemeModel is already registered, and the enum is declared using Q_ENUM.

I haven't tracked down which commit introduced the regression, nor why this is not registered properly, as far as I know this is the only enum causing problems (maybe because this is the only enum propagated through signals outside its parent class)