gnome-session: Make sure REGION is not confused by debug output
When gnome-session is invoked with G_MESSAGES_DEBUG=all set, $REGION will also contain dconf's debug output:
$ G_MESSAGES_DEBUG=all gsettings get org.gnome.system.locale region
(process:14005): dconf-DEBUG: 15:59:46.581: watch_fast: "/system/locale/" (establishing: 0, active: 0)
'de_DE.UTF-8'
(process:14005): dconf-DEBUG: 15:59:46.582: unwatch_fast: "/system/locale/" (active: 0, establishing: 1)
Avoid that by setting G_MESSAGES_DEBUG empty.