use GC'ed strings when calling into the script engine
use GC'ed strings when calling into the script engine

Thanks Radosław Szkodziński for noticing

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