Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: use-after-free information disclosure in createsaverwindow()

A use-after-free flaw was found in the X.Org X server and Xwayland in CreateSaverWindow(). A client can trigger a use-after-free read after changing window attributes and forcing the screen saver, leading to information disclosure.