In English, there is an understanding that a double negative equals a positive.
Your example:
Nothing bad wouldn't happen...
means everything that is bad would happen. Why? No thing which is bad would not happen.
The idiom is common in English as well. Often it's expressed either way, it's ok, or either way, it's good.
"Bad publicity or good publicity, it still exposes people to our mission. Either way, it's good."
If yes, ok; if not, nothing bad will happen, right? (punctuation edited)
is fine, as you did not use a double negative here. The not is separated from nothing. For a more common expression, make the last part a positive instead of a non-negative:
If yes, great; if not, it's still good, right?