avfilter: remove unneeded check

If link->src were NULL, it would have crashed earlier.
Makes coverity less confused.

CC: libav-stable@libav.org
Bug-Id: CID 700371
vf_unsharp: always initialize array with something

CC: libav-stable@libav.org
Bug-Id: CID 732298
vf_format: avoid null pointer dereference

CC: libav-stable@libav.org
Bug-Id: CID 1224280
vf_showinfo: check negative index

CC: libav-stable@libav.org
Bug-Id: CID 1087086
af_resample: check av_opt_set_dict return value

CC: libav-stable@libav.org
Bug-Id: CID 1087076
audiointerleave: check av_new_packet return value

CC: libav-stable@libav.org
Bug-Id: CID 1087078
avio: fix sizeof argument

CC: libav-stable@libav.org
Bug-Id: CID 732284
aviobuf: check context before using it

Avoid a possible null pointer dereference.

CC: libav-stable@libav.org
Bug-Id: CID 1135769
network: check return values

ff_socket_nonblock wraps fcntl.

CC: libav-stable@libav.org
Bug-Id: CID 1026742 / CID 1026743 /CID 1026744 / CID 1087075
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
nutdec: Prevent a memory corruption

Chapters do not have an event_flags field.

Bug-Id: CID 1231990
nutdec: check av_new_packet return value

CC: libav-stable@libav.org
Bug-Id: CID 733713
nutenc: check for negative index rather than assert

CC: libav-stable@libav.org
Bug-Id: CID 703721
matroskadec: fix leak on error

CC: libav-stable@libav.org
Bug-Id: CID 1026767
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