[webgui] handle special case also for qt6
[webgui] handle special case also for qt6

It is workaround to show qt5/qt6 widgets inside parent window
without need to instantiate RWebDisplayArgs class
olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root