Empty Set-Cookie header

The current (as of 2.3.5) ActionController::Response#convert_cookies! method generates an empty Set-Cookie header if there aren't any cookies. This gets caught by (at least) thin and webrick. Both remove the empty Set-Cookie header line. However unicorn doesn't and I think it's Rails responsibility to not generate a header like this. Changing the convert_cookies! method to something like this fixes the problem:

def convert_cookies!
  cs = Array(headers['Set-Cookie']).compact
  headers['Set-Cookie'] = cs unless cs.empty?
end