[gdm] launch-environment: don't name greeter log $display-greeter.log with user displays

[Ray Strode <halfline src gnome org>]

commit 10418ea982f91f62a5052177578de2ecc3597317
Author: Ray Strode <rstrode redhat com>
Date:   Thu Sep 21 09:50:00 2017 -0400

    launch-environment: don't name greeter log $display-greeter.log with user displays
    
    If the X server is started as part of the session, we don't know the
    display up front. So don't try to encode the display in the log in that
    case.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=787989

 daemon/gdm-launch-environment.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/daemon/gdm-launch-environment.c b/daemon/gdm-launch-environment.c
index 5fd346f..676ebc6 100644
--- a/daemon/gdm-launch-environment.c
+++ b/daemon/gdm-launch-environment.c
@@ -285,7 +285,11 @@ on_conversation_started (GdmSession           *session,
         char             *log_path;
         char             *log_file;
 
-        log_file = g_strdup_printf ("%s-greeter.log", launch_environment->priv->x11_display_name);
+        if (launch_environment->priv->x11_display_name != NULL)
+                log_file = g_strdup_printf ("%s-greeter.log", launch_environment->priv->x11_display_name);
+        else
+                log_file = g_strdup ("greeter.log");
+
         log_path = g_build_filename (LOGDIR, log_file, NULL);
         g_free (log_file);