[mutter] monitor-manager: Fix crash when UPower is not available

[Bastien Nocera <hadess src gnome org>]

commit f5f0ff0a2ff23f6fbada45d6e8d297074974f339
Author: Bastien Nocera <hadess hadess net>
Date:   Wed May 31 15:17:01 2017 +0200

    monitor-manager: Fix crash when UPower is not available
    
    Don't access the upower client if it doesn't exist
    
    https://bugzilla.gnome.org/show_bug.cgi?id=780407

 src/backends/meta-monitor-manager.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/backends/meta-monitor-manager.c b/src/backends/meta-monitor-manager.c
index 682a14b..3e35058 100644
--- a/src/backends/meta-monitor-manager.c
+++ b/src/backends/meta-monitor-manager.c
@@ -375,6 +375,9 @@ lid_is_closed_changed (UpClient   *client,
 static gboolean
 meta_monitor_manager_real_is_lid_closed (MetaMonitorManager *manager)
 {
+  if (!manager->up_client)
+    return FALSE;
+
   return up_client_get_lid_is_closed (manager->up_client);
 }