Fix termination of mov_ch_layouts_wav array lookup

Problem found using ASAN.
In some case, the ff_mov_get_channel_layout_tag function will not find 0
as termination for lookup in the array mov_ch_layouts_wav.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
segment: copy metadata

Fixes Ticket2230

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>