title: Internal Server Error 500 while accessing $GITLAB/admin/runners
body: <p>I have restored Gitlab from a backup, now every time I try to access the <code>runners</code> webpage, I get a Internal Server error.</p>
  
  <p>I have tried uninstalling all configured gitlab-runners and accessing it, the problem persists. Here is a trace from the gitlab-rails/production.log:</p>
  
  <pre><code>Started GET "/admin/runners" for 127.0.0.1 at 2019-01-16 07:17:12 -0500
  Processing by Admin::RunnersController#index as HTML
  Completed 500 Internal Server Error in 66ms (ActiveRecord: 5.7ms)
  
  ActionView::Template::Error ():
      37: 
      38:     .col-sm-6
      39:       .bs-callout
      40:         = render partial: 'ci/runner/how_to_setup_runner',
      41:                  locals: { registration_token: Gitlab::CurrentSettings.runners_registration_token,
      42:                            type: 'shared',
      43:                            reset_token_url: reset_registration_token_admin_application_settings_path }
  
  lib/gitlab/crypto_helper.rb:27:in `aes256_gcm_decrypt'
  app/models/concerns/token_authenticatable_strategies/encrypted.rb:55:in `get_token'
  app/models/concerns/token_authenticatable_strategies/base.rb:33:in `ensure_token!'
  app/models/concerns/token_authenticatable.rb:43:in `block in add_authentication_token_field'
  app/models/application_setting.rb:409:in `runners_registration_token'
  lib/gitlab/current_settings.rb:19:in `method_missing'
  app/views/admin/runners/index.html.haml:40:in `_app_views_admin_runners_index_html_haml___977288809002382166_69944849285200'
  app/controllers/application_controller.rb:116:in `render'
  lib/gitlab/i18n.rb:55:in `with_locale'
  lib/gitlab/i18n.rb:61:in `with_user_locale'
  app/controllers/application_controller.rb:420:in `set_locale'
  lib/gitlab/middleware/multipart.rb:103:in `call'
  lib/gitlab/request_profiler/middleware.rb:16:in `call'
  lib/gitlab/middleware/go.rb:19:in `call'
  lib/gitlab/etag_caching/middleware.rb:13:in `call'
  lib/gitlab/middleware/correlation_id.rb:16:in `block in call'
  lib/gitlab/correlation_id.rb:15:in `use_id'
  lib/gitlab/middleware/correlation_id.rb:15:in `call'
  lib/gitlab/middleware/read_only/controller.rb:40:in `call'
  lib/gitlab/middleware/read_only.rb:18:in `call'
  lib/gitlab/middleware/basic_health_check.rb:25:in `call'
  lib/gitlab/request_context.rb:20:in `call'
  lib/gitlab/metrics/requests_rack_middleware.rb:29:in `call'
  lib/gitlab/middleware/release_env.rb:13:in `call'
  Started GET "/-/metrics" for 127.0.0.1 at 2019-01-16 07:17:24 -0500
  Processing by MetricsController#index as HTML
  Completed 200 OK in 1ms (Views: 0.4ms | ActiveRecord: 0.0ms)
  
  </code></pre>