libhb: fix "missing start code" error message when encoding BD
CC subtitles which are embedded in the video stream have an id
of 0 assigned.  We should ignore these when setting up the PID
filter list since they do not use an independent PID.


git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5860 b64f7644-9d1e-0410-96f1-a4d463321fa5