Spree - 未定义的局部变量或方法`meta_data_tags'错误

Question

我在layouts/application.html.erb档案

中有这一行

<%== meta_data_tags unless content_for? :head %>

我正在

  

未定义的局部变量或方法`meta_data_tags'

错误

我的apllication_controller.rb

  class ApplicationController < ActionController::Base
    include Spree::Core::Engine.routes.url_helpers
    include Spree::Core::Engine.helpers
    include Spree::Core::ControllerHelpers
    include Spree::AuthenticationHelpers
  end

有人可以帮我解决这个问题吗？

$ spree version
2.2.13

$ rails -v
Rails 4.0.13

$ ruby -v
ruby 2.1.8p440 (2015-12-16 revision 53160) [x86_64-linux]

提前致谢