Fix bug.

config/routes.rb

@@ -70,6 +70,7 @@ Rails.application.routes.draw do
         post 'del_file', to: 'application_forms#del_file'
       end
     end
+    get '/xhr/application_forms/check_availability', to: 'application_forms#check_availability'
     get '/xhr/application_forms/agree_link' , to: 'application_forms#agree_link'
   end