[gnome-settings-daemon] power: Assert on error if mock external screens are used

[Bastien Nocera <hadess src gnome org>]

commit 9be264f85600bed42de159e8511a3f02f93a6164
Author: Bastien Nocera <hadess hadess net>
Date:   Tue Apr 16 16:22:41 2013 +0200

    power: Assert on error if mock external screens are used

 plugins/power/gpm-common.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/plugins/power/gpm-common.c b/plugins/power/gpm-common.c
index ec8b778..55736ad 100644
--- a/plugins/power/gpm-common.c
+++ b/plugins/power/gpm-common.c
@@ -1705,11 +1705,13 @@ external_monitor_is_connected (GnomeRRScreen *screen)
                        return FALSE;
                }
 
-               g_warning ("Unhandled value for GSD_MOCK_EXTERNAL_MONITOR contents: %s", 
mock_external_monitor_contents);
+               g_error ("Unhandled value for GSD_MOCK_EXTERNAL_MONITOR contents: %s", 
mock_external_monitor_contents);
                g_free (mock_external_monitor_contents);
        }
 #endif /* GSD_MOCK */
 
+       g_assert (screen != NULL);
+
         /* see if we have more than one screen plugged in */
         outputs = gnome_rr_screen_list_outputs (screen);
         for (i = 0; outputs[i] != NULL; i++) {