libvlc_media_list: missing vlc_mutex_destroy

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

lib/media_list.c

@@ -220,6 +220,7 @@ void libvlc_media_list_release( libvlc_media_list_t * p_mlist )
     }
 
     vlc_mutex_destroy( &p_mlist->object_lock );
+    vlc_mutex_destroy( &p_mlist->refcount_lock );
     vlc_array_clear( &p_mlist->items );
 
     free( p_mlist );