[atk] Nullify the gobject cache accessible when the accessible is finalized.

[Alejandro Piñeiro Iglesias <apinheiro src gnome org>]

commit 1838235ac65ddf47dcd434ef8cbb6cc11ce96699
Author: Alban Browaeys <prahal yahoo com>
Date:   Mon Apr 29 21:27:23 2013 +0200

    Nullify the gobject cache accessible when the accessible is finalized.
    
    When the gobject is disposed the weak reference finalize
    the accessible. But the gobject could still be reference
    thus not finalized. As the gobject still holds the accessible
    in its qdata, next call to atk_gobject_accessible_for_object
    returns the old accessible freed memory. If the caller attempts
    to do anything with this memory as if an atkobject it segfaults.
    
    This happens here : gnome-shell segfault when the password prompt
    it generates is triggered more than once. As the clutter stage still
     holds a reference to the StIMText, which wasdisposed when the
     password widget was destroyed with the end of the first password
    widget, when the second password prompt attempt notify key focus to the
    old widget, it gets its accessible (now freed memory) via the StIMText
    qdata cache, and pass this to atk_object_notify_state_change.
    
    gobject still hold a pointer to it via qdata.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=699262

 atk/atkgobjectaccessible.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/atk/atkgobjectaccessible.c b/atk/atkgobjectaccessible.c
index ba87480..eb0bf09 100644
--- a/atk/atkgobjectaccessible.c
+++ b/atk/atkgobjectaccessible.c
@@ -140,8 +140,14 @@ atk_real_gobject_accessible_initialize (AtkObject  *atk_obj,
 static void
 atk_gobject_accessible_dispose (gpointer  data)
 {
+  GObject *object;
+
   g_return_if_fail (ATK_IS_GOBJECT_ACCESSIBLE (data));
 
+  object = atk_gobject_accessible_get_object (data);
+  if (object)
+      g_object_set_qdata (object, quark_accessible_object, NULL);
+
   g_object_set_qdata (G_OBJECT (data), quark_object, NULL);
   atk_object_notify_state_change (ATK_OBJECT (data), ATK_STATE_DEFUNCT,
                                   TRUE);