[gnome-settings-daemon] xrandr: Fix warning on exit

[Bastien Nocera <hadess src gnome org>]

commit 4c76f0bff8f78fca0830138ffe2d0e7acf4cfb87
Author: Bastien Nocera <hadess hadess net>
Date:   Thu Oct 13 12:13:12 2016 +0200

    xrandr: Fix warning on exit
    
    If _stop() is called twice, we would pass an already freed ID to
    g_bus_unown_name().
    
    gsd-xrandr[1874]: Invalid id 1 passed to g_bus_unown_name()

 plugins/xrandr/gsd-xrandr-manager.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/plugins/xrandr/gsd-xrandr-manager.c b/plugins/xrandr/gsd-xrandr-manager.c
index 06906a9..c31976b 100644
--- a/plugins/xrandr/gsd-xrandr-manager.c
+++ b/plugins/xrandr/gsd-xrandr-manager.c
@@ -1289,8 +1289,10 @@ gsd_xrandr_manager_stop (GsdXrandrManager *manager)
                 manager->priv->upower_client = NULL;
         }
 
-        if (manager->priv->name_id != 0)
+        if (manager->priv->name_id != 0) {
                 g_bus_unown_name (manager->priv->name_id);
+                manager->priv->name_id = 0;
+        }
 
         if (manager->priv->introspection_data) {
                 g_dbus_node_info_unref (manager->priv->introspection_data);