Serialize vlc_object_set_destructor() against vlc_object_release()

(cherry picked from commit 6fa0eee4)

src/misc/objects.c

@@ -279,7 +279,10 @@ void __vlc_object_set_destructor( vlc_object_t *p_this,
                                   vlc_destructor_t pf_destructor )
 {
     vlc_object_internals_t *p_priv = vlc_internals(p_this );
+
+    vlc_spin_lock( &p_priv->ref_spin );
     p_priv->pf_destructor = pf_destructor;
+    vlc_spin_unlock( &p_priv->ref_spin );
 }
 
 /**