Merge branch 'rails5-fix-47805' into 'master'

Rails5 ActionController::ParameterMissing: param is missing or the value is…

Closes #47805

See merge request gitlab-org/gitlab-ce!19763

changelogs/unreleased/rails5-fix-47805.yml

+---
+title: 'Rails5 ActionController::ParameterMissing: param is missing or the value is
+  empty: application_setting'
+merge_request: 19763
+author: Jasper Maes
+type: fixed

spec/controllers/admin/application_settings_controller_spec.rb

@@ -73,7 +73,7 @@ describe Admin::ApplicationSettingsController do
     end
 
     it 'updates the restricted_visibility_levels when empty array is passed' do
-      put :update, application_setting: { restricted_visibility_levels: [] }
+      put :update, application_setting: { restricted_visibility_levels: [""] }
 
       expect(response).to redirect_to(admin_application_settings_path)
       expect(ApplicationSetting.current.restricted_visibility_levels).to be_empty