I want install redmine plugin ldap_sync, but when i test it, i have error:

Completed 500 Internal Server Error in 28ms (ActiveRecord: 19.6ms)
NoMethodError (undefined method `fetch' for nil:NilClass):

so thats part of code, which have some fetch

...
 def test
    return render 'ldap_setting_invalid' unless @ldap_setting.valid?

    ldap_test = params[:ldap_test]
    users     = ldap_test.fetch(:test_users, '').split(',')
    groups    = ldap_test.fetch(:test_groups, '').split(',')
    [users, groups].each {|l| l.map(&:strip).reject(&:blank?) }


    @test = LdapTest.new(@ldap_setting)
    @test.bind_user = ldap_test[:bind_user]
    @test.bind_password = ldap_test[:bind_password]

    if @test.valid?
      @test.run_with_users_and_groups(users, groups)
    else
      render 'ldap_test_invalid'
    end
  end
...

so thats part of code, which have some fetch in redmine plugin:

...
 def test
    return render 'ldap_setting_invalid' unless @ldap_setting.valid?

    ldap_test = params[:ldap_test]
    users     = ldap_test.fetch(:test_users, '').split(',')
    groups    = ldap_test.fetch(:test_groups, '').split(',')
    [users, groups].each {|l| l.map(&:strip).reject(&:blank?) }


    @test = LdapTest.new(@ldap_setting)
    @test.bind_user = ldap_test[:bind_user]
    @test.bind_password = ldap_test[:bind_password]

    if @test.valid?
      @test.run_with_users_and_groups(users, groups)
    else
      render 'ldap_test_invalid'
    end
  end
...