make swfdec_as_object_mark() only mark if not marked yet
make swfdec_as_object_mark() only mark if not marked yet

mltframework/swfdec,freedesktop-unofficial-mirror/swfdec__swfdec,freedesktop-unofficial-mirror/swfdec__swfdec,freedesktop-unofficial-mirror/swfdec__swfdec,mltframework/swfdec