Ruby CSV追記時に"no implicit conversion of nil into String (TypeError)"というエラーが出る

■分からないこと
RubyのNokogiriを使ってスクレイピングをしようとしています。
要素の抽出は出来てまして、それをcsvに追記しようとすると"no implicit conversion of nil into String (TypeError)"とエラーが出てしまいます。
原因を教えていただければ幸いです。

■エラー内容

F, [2020-01-01T15:52:28.365797 #3427] FATAL -- : no implicit conversion of nil into String (TypeError)
/Users/ryo/.rbenv/versions/2.6.0/lib/ruby/2.6.0/csv.rb:638:in `initialize'
/Users/ryo/.rbenv/versions/2.6.0/lib/ruby/2.6.0/csv.rb:638:in `open'
/Users/ryo/.rbenv/versions/2.6.0/lib/ruby/2.6.0/csv.rb:638:in `open'
get_baitoru.rb:27:in `get_params'
get_baitoru.rb:43:in `main'
get_baitoru.rb:53:in `<main>'

■コード

def get_params
  begin
    uri = "https://www.baitoru.com/kanto/jlist/tokyo/hotel-guestroomclean/"
    html = open(uri).read
    document = Nokogiri::HTML(html.toutf8, nil, 'utf-8')
    names = []
    job_No = []
    created_date = []

    cnt = 0
    (1..20).to_a.each do |idx|
      names = document.xpath("//*[@id='link_job_detail_pc_jlist_all_p_#{idx}_20']/div/div[2]/div[2]/p").text.to_s
      job_No = document.xpath("//*[@id='async_content2']/article[#{idx}]/div/div[3]/p/text()").text.to_s
      created_date = Date.today

      CSV.open(@fliename, "a", write_headers: true) do |csv|
        csv << [names,job_No,created_date]
      end

      @stdout.info("working on #{names} count #{cnt}")
      cnt = cnt + 1
    end
  rescue => e
    @stdout.fatal(e)
  end
end

def main()
  headers = ['name','job_No','created_date']
  @title = 'baitoru'
  time = Time.new.strftime("%Y_%m_%d")
  @filename = "#{@title}_new_#{time}.csv"
  CSV.open(@filename, "w", write_headers: true) {|csv| csv << headers }
  @stdout.info("#{@title}_new_#{time}.csv is created")

  get_params

end

if __FILE__ == $0
  @stdout = Logger.new(STDOUT)

  @stdout.info('process started')
  main()
  @stdout.info('process finished')
end