Removes code duplication (code climate)

No gain but it's "better": https://codeclimate.com/github/Mogztter/asciidoctor/compare/code-climate
> And if colspec is nil or empty that won't be a problem either ?

No, read me note in the previous comment.

> …we put something in to remove it later.

I don’t see it as a problem, since it makes the code more clean and readable.