How to beat "First argument in form" error in GitLab?

Question

Ruby on Rails

Self-assembled Gitlab started up. However, when trying to access the /gitlab/admin/application_settings page from a valid admin panel, the following error occurs (it seems from Rails):

Started GET "/gitlab/admin/application_settings" for <IP> at 2018-06-16 19:29:24 +0000
Processing by Admin::ApplicationSettingsController#show as HTML
Completed 500 Internal Server Error in 11ms (ActiveRecord: 1.3ms)

ActionView::Template::Error (First argument in form cannot contain nil or be empty):
    1: = form_for @application_setting, url: admin_application_settings_path, html: { class: 'fieldset-form' } do |f|
    2:   = form_errors(@application_setting)
    3: 
    4:   %fieldset
  app/views/admin/application_settings/_visibility_and_access.html.haml:1:in `_app_views_admin_application_settings__visibility_and_access_html_haml___3591089777756656369_47400957548000'
  app/views/admin/application_settings/show.html.haml:15:in `_app_views_admin_application_settings_show_html_haml__337089356688845664_47400870709080'
  lib/gitlab/i18n.rb:50:in `with_locale'
  lib/gitlab/i18n.rb:56:in `with_user_locale'
  app/controllers/application_controller.rb:362:in `set_locale'
  lib/gitlab/middleware/multipart.rb:95:in `call'
  lib/gitlab/request_profiler/middleware.rb:14:in `call'
  lib/gitlab/middleware/go.rb:17:in `call'
  lib/gitlab/etag_caching/middleware.rb:11:in `call'
  lib/gitlab/middleware/read_only/controller.rb:28:in `call'
  lib/gitlab/middleware/read_only.rb:16:in `call'
  lib/gitlab/request_context.rb:18:in `call'
  lib/gitlab/metrics/requests_rack_middleware.rb:27:in `call'
  lib/gitlab/middleware/release_env.rb:10:in `call'

What it is? How can you win? I really don't want to learn Ruby anymore)))

Answer 1

The variable @application_settingmost likely has an illegal value nil.
It is worth addressing the same question to GitLab support , since only those who write and understand their code can help here.