QWSServer::screenSaverActivate(true) does not call custom screensaver

Calling QWSServer::screenSaverActivate(true) ignores an installed custom screensaver object and uses QWSServerPrivate::_q_screenSaverSleep() to directly call blank() of the installed screen driver, which results in a blank display instead of whatever QScreenSaver::save() is supposed to do. Deactivation works fine.
Attached is a patch that calls QWSServerPrivate::_q_screenSaverTimeout() instead to achieve the expected behaviour, at least for a screensaver with one single level. Not tested with multi-level savers.