Gui: [skip ci] simplify Application::setStyleSheet and directly check if the passed file name exists
Gui: [skip ci] simplify Application::setStyleSheet and directly check if the passed file name exists

Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master