g_dbus_action_group_changed: don't leak iterator and its contents

Signed-off-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
Bug: https://bugzilla.gnome.org/show_bug.cgi?id=666113
Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>

gio/gdbusactiongroup.c

@@ -229,6 +229,7 @@ g_dbus_action_group_changed (GDBusConnection *connection,
             else
               action_info_free (info);
           }
+        g_variant_iter_free (iter);
       }
     }
 }