[at-spi2-core] Add a check NULL of the source accessible handling an event

[Mike Gorse <mgorse src gnome org>]

commit 87edad3524073d5e478a9b5aa33ad4bb4700e444
Author: Alejandro Piñeiro <apinheiro igalia com>
Date:   Fri Mar 14 11:43:19 2014 +0100

    Add a check NULL of the source accessible handling an event
    
    https://bugzilla.gnome.org/show_bug.cgi?id=726243

 atspi/atspi-event-listener.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/atspi/atspi-event-listener.c b/atspi/atspi-event-listener.c
index 752d440..09ccfd3 100644
--- a/atspi/atspi-event-listener.c
+++ b/atspi/atspi-event-listener.c
@@ -995,6 +995,11 @@ _atspi_dbus_handle_event (DBusConnection *bus, DBusMessage *message, void *data)
   }
   e.type = converted_type;
   e.source = _atspi_ref_accessible (dbus_message_get_sender(message), dbus_message_get_path(message));
+  if (e.source == NULL)
+  {
+    g_warning ("Got no valid source accessible for signal for signal %s from interface %s\n", member, 
category);
+    return DBUS_HANDLER_RESULT_HANDLED;
+  }
 
   dbus_message_iter_recurse (&iter, &iter_variant);
   switch (dbus_message_iter_get_arg_type (&iter_variant))