[glib] Avoid a segfault in gdbus tool

[Matthias Clasen <matthiasc src gnome org>]

commit b382c6f63339397c338aa68ad939894665368ada
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat May 25 23:07:03 2013 -0400

    Avoid a segfault in gdbus tool
    
    When the interface name is invalid, we don't get an error
    back from g_dbus_connection_call_sync.

 gio/gdbus-tool.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/gio/gdbus-tool.c b/gio/gdbus-tool.c
index 01a6c68..2714dd7 100644
--- a/gio/gdbus-tool.c
+++ b/gio/gdbus-tool.c
@@ -1017,8 +1017,11 @@ handle_call (gint        *argc,
                                         &error);
   if (result == NULL)
     {
-      g_printerr (_("Error: %s\n"), error->message);
-      g_error_free (error);
+      if (error)
+        {
+          g_printerr (_("Error: %s\n"), error->message);
+          g_error_free (error);
+        }
       if (in_signature_types != NULL)
         {
           GString *s;