PVS-Studio warning V557 for FFMpeg

void ff_mjpeg_encode_mb(MpegEncContext *s,
                        int16_t block[6][64])
{
    int i;
    if (s->chroma_format == CHROMA_444) {
        encode_block(s, block[0], 0);
        encode_block(s, block[2], 2);
        encode_block(s, block[4], 4);
        encode_block(s, block[8], 8);
        encode_block(s, block[5], 5);
        encode_block(s, block[9], 9);
  ....
}

This suspicious code was found in FFMpeg project by PVS-Studio static code analyzer.
Warning message is:
V557 Array overrun is possible. The '8' index is pointing beyond array bound. mjpegenc.c 497

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/