Merge branch 'blackst0ne-rails5-fix-application-settings-controller' into 'master'

[Rails5] Fix admin/application_settings_controller

See merge request gitlab-org/gitlab-ce!18275

app/controllers/admin/application_settings_controller.rb

@@ -56,7 +56,9 @@ class Admin::ApplicationSettingsController < Admin::ApplicationController
   end
   def application_setting_params
+    params[:application_setting] ||= {}
     import_sources = params[:application_setting][:import_sources]
+
     if import_sources.nil?
       params[:application_setting][:import_sources] = []
     else