don't assert a movie exists in open
don't assert a movie exists in open

There might not be one, as opening can happen way later than creating
the movie and lots of stuff can have happened

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