changed it so that 0 is counted as a short vector. This seems to have been
causing some issues where birthday sieve would not make progress.
Also, if the vector is too long it isn't added to the second list.
We still have the problem of the relative lengths of birthday sieve lists
always being either very long or short even though they should be totally
random or at least consistent, while they are currently not at all consistent
within difference instances of the program