Chromium fuzzing produced a whacky file with extra tkhds. This caused
an AVStream that was already in use to be corrupted by assigning it a
new id, which blows up later in mov_read_trun because the
MOVFragmentStreamInfo.index_entry now points OOB.
Reviewed-by: Baptiste Coudurier <baptiste.coudurier@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>