No audio stream is created unconditionally and if none has been created,
no packet with stream_index 1 may be returned. This fixes an assert in
ff_read_packet() in libavformat/utils reported in ticket #8782.
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
(cherry picked from commit ec59dc73f0cc8930bf5dae389cd76d049d537ca7)
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>