If an audio stream is present, the Sega FILM muxer checks for its
compability with the container during init, so that the very same check
needn't be repeated during writing the trailer.

Essentially the same is true for the presence of a video stream: It has
already been checked during init. Furthermore, after the check for the
presence of a video stream succeeded, a pointer is set to point to the
video stream. Yet said pointer (which was NULL before) will be
derefenced anyway regardless of the result of the check. Coverity thus
complained about this in CID 1434155 and removing this pointless check
will also fix this issue.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>