Check for `length(wv)`

[davidavdav]

https://github.com/JuliaStats/StatsBase.jl/blob/0ea8e798c3d19609ed33b11311de5a2bd6ee9fd0/src/counts.jl#L46

I think you should check for the length of wv, since you're using @inbounds later

[nalimilan]

Good catch. Do you feel like making a PR?

[davidavdav]

OK, done, I saw that there are a few places where <= could be a ≤ and a = could be a in, but this is a different kind of thing...