matroskadec: check return values

CC: libav-stable@libav.org
Bug-Id: CID 733712
matroskadec: error out if embl doctype is not set

Avoid a null pointer dereference.

CC: libav-stable@libav.org
Bug-Id: CID 1087083
mpegaudio_tablegen: refactor to avoid casting

CC: libav-stable@libav.org
Bug-Id: CID 1238835
mpeg12enc: factor out check in encode_dc

Makes coverity less confused.

CC: libav-stable@libav.org
Bug-Id: CID 751744
mpegvideo_enc: rework direct mode check

Remove stray semicolon and share codepaths.

CC: libav-stable@libav.org
Bug-Id: CID 991857
mpegvideo: check mpv return value

CC: libav-stable@libav.org
Bug-Id: CID 1238786
mpegvideo_parser: check ff_set_dimensions return value

Also correctly propagate errors to mpegvideo_parse.

CC: libav-stable@libav.org
Bug-Id: CID 1135741
4xm: drop unnecessary check

data_size is always >= 0 in this case.

CC: libav-stable@libav.org
Bug-Id: CID 1238788
4xm: more thorought check for negative index and negative shift

CC: libav-stable@libav.org
Bug-Id: CID 1087094
rtp: Free the addrinfo pointer on failure

CC: libav-stable@libav.org
Bug-Id: CID 1238797
rtspdec: check strchr return value

CC: libav-stable@libav.org
Bug-Id: CID 1041130
rtpdec_hevc: drop unnecessary check

len is always >=1 in that case.

Bug-Id: CID 1238784
rtpenc: check mb_info return value before using it

CC: libav-stable@libav.org
Bug-Id: CID 1035715
rtmpproto: remove dead code

Expression already evaluated before, redundant since
053386864219eccbcca1886c55f902f9555428a5.

Bug-Id: CID 732199
display: fix order of operands

CC: libav-stable@libav.org
Bug-Id: CID 1238828 / CID 1238832
swf: prevent theoretical double free

CC: libav-stable@libav.org
Bug-Id: CID 602000
motion_est: error out on negative index

CC: libav-stable@libav.org
Bug-Id: CID 29387
idcin: fix return check

CC: libav-stable@libav.org
Bug-Id: CID 732198
mov: fix assigment check

CC: libav-stable@libav.org
Bug-Id: CID 1197050
dnxhdenc: check negative index

CC: libav-stable@libav.org
Bug-Id: CID 700464