[at-spi2-core] Add a check for a null message when returning a hyperlink

[Mike Gorse <mgorse src gnome org>]

commit 324fb3422c5fd8f96cae51d4f37812eee33078de
Author: Mike Gorse <mgorse suse com>
Date:   Mon May 7 11:28:05 2012 -0500

    Add a check for a null message when returning a hyperlink

 atspi/atspi-misc.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/atspi/atspi-misc.c b/atspi/atspi-misc.c
index 37971cf..6589843 100644
--- a/atspi/atspi-misc.c
+++ b/atspi/atspi-misc.c
@@ -611,8 +611,12 @@ _atspi_dbus_return_hyperlink_from_message (DBusMessage *message)
 {
   DBusMessageIter iter;
   AtspiHyperlink *retval = NULL;
-  const char *signature = dbus_message_get_signature (message);
+  const char *signature;
    
+  if (!message)
+    return NULL;
+
+  signature = dbus_message_get_signature (message);
   if (!strcmp (signature, "(so)"))
   {
     dbus_message_iter_init (message, &iter);