[at-spi2-core] Avoid dereferencing a null message

[Mike Gorse <mgorse src gnome org>]

commit 24ccba3a9caaa527e0f9f60f24641c10005afc21
Author: Mike Gorse <mgorse novell com>
Date:   Mon Sep 19 15:43:42 2011 -0500

    Avoid dereferencing a null message

 atspi/atspi-event-listener.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/atspi/atspi-event-listener.c b/atspi/atspi-event-listener.c
index f0a4ad8..83c9ae0 100644
--- a/atspi/atspi-event-listener.c
+++ b/atspi/atspi-event-listener.c
@@ -693,7 +693,8 @@ atspi_event_listener_deregister_from_callback (AtspiEventListenerCB callback,
       return FALSE;
       dbus_message_append_args (message, DBUS_TYPE_STRING, &event_type, DBUS_TYPE_INVALID);
       reply = _atspi_dbus_send_with_reply_and_block (message, error);
-      dbus_message_unref (reply);
+      if (reply)
+        dbus_message_unref (reply);
 
       listener_entry_free (e);
     }