WordSubstitutionModel bug

[Connor McCoy]

Hi All,

I've been trying to use bpp::WordSubstitutionModel in a project, and think I've found a bug - a `size_t` is decremented from 0, which on my machine becomes a very large number and causes a segfault.

Patch attached, and also viewable here: http://cl.ly/code/3t2Z2J2n1I2Q

Thanks!

Connor

[Laurent Guéguen]

Hi Connor,

yes indeed, thanks a lot for the fix, I push it.

Cheers,
L