avcodec/indeo3: check the return code of ff_set_dimensions()

This is currently redundant as the checks before it are tighter than
the checks in ff_set_dimensions() but its more robust not to depend
on that.

Fixes CID1135740
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/pthread_frame: Fix memleak of AVCodecContext on error

Fixes CID1135767
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/snowdec: check av_frame_ref() return value

Fixes CID1135742

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