avcodec/libutvideoenc: fix leak of info array on error

Fixes CID1257657

Reviewed-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/libutvideoenc: Check avpicture_get_size() return code

Fixes CID1257656

Reviewed-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>