Fix index incremented when it shouldn't be
Fix index incremented when it shouldn't be

Index i should only be incremented after b[i] is set.
Otherwise we get some b[i] that always contains 0.

License: MIT
Signed-off-by: Christian Couder <ddbaab5867ed34fd53535b58c9cdd59abd2e2aff@tuxfamily.org>

jbenet/go-random