Fix bug: users can now be saved

lib/central_server_exchange_app.rb

@@ -31,8 +31,8 @@ class CentralServerExchangeApp < Sinatra::Base
   post '/purchase/design' do
     begin
       private_key = OpenSSL::PKey::RSA.new(@site.private_key)
-      design = PDesign.new.from_json(private_key.private_decrypt(request.params['purchase']))
-      design.save
+      p_design = PDesign.new.from_json(private_key.private_decrypt(request.params['purchase']))
+      p_design.save
       body 'true'
     rescue
       body 'false'