[gdm] Only strip CK goo from seat prefix, if there's CK goo in seat prefix

[Ray Strode <halfline src gnome org>]

commit 59f883f28a4b176cb821e4ee2aaec4f024e22213
Author: Ray Strode <rstrode redhat com>
Date:   Mon Apr 9 14:01:22 2012 -0400

    Only strip CK goo from seat prefix, if there's CK goo in seat prefix
    
    Now that we can use logind for seat management, there' may not be
    /org/freedesktop/ConsoleKit in the seat identifier.
    
    This commit makes sure the GDM_SEAT_ID environment variable doesn't
    show gunk in the case the system is configured to use logind.
    
    Related downstream report:
    
    http://bugzilla.redhat.com/810451

 daemon/gdm-welcome-session.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/daemon/gdm-welcome-session.c b/daemon/gdm-welcome-session.c
index 01df365..d0ca4e6 100644
--- a/daemon/gdm-welcome-session.c
+++ b/daemon/gdm-welcome-session.c
@@ -308,8 +308,9 @@ build_welcome_environment (GdmWelcomeSession *welcome_session,
         if (start_session && welcome_session->priv->x11_display_seat_id != NULL) {
                 char *seat_id;
 
-                seat_id = welcome_session->priv->x11_display_seat_id +
-                        strlen ("/org/freedesktop/ConsoleKit/");
+                if (g_str_has_prefix (welcome_session->priv->x11_display_seat_id, "/org/freedesktop/ConsoleKit/")) {
+                        seat_id = welcome_session->priv->x11_display_seat_id + strlen ("/org/freedesktop/ConsoleKit/");
+                }
 
                 g_hash_table_insert (hash, g_strdup ("GDM_SEAT_ID"), g_strdup (seat_id));
         }