Out of range exception for --block = 3 and 7 and --halving

[petrs]

Hi, the booltest will fail when run for quite small block lengths:

>booltest --block 7 --halving data.bin

\booltest\booltest_main.py", line 1110, in print_human_readable_results
    dist = inp['res'][0]['dists'][0]
IndexError: list index out of range

[ph4r05]

Thanks for report. If I collect enough mental mana I may fix it. But as this is a bit degenerate case of the blocksize I am thinking about marking this as "won't fix".