gtkapplication-dbus: Initialise screensaver-active property
When GtkApplication starts listening to the screensaver's D-Bus status, the screensaver-active property is not initialised and applications making use of the property are out of sync until the first state change. Any application starting when the screensaver is active will think it's inactive.
To fix this, we set the property when we first start monitoring the screensaver.
Upstream MR: https://gitlab.gnome.org/GNOME/gtk/merge_requests/1091
Edited by Bob Ham