当在 Recaptcha 中键入关键字没问题时,我总是会弹出这个空白的 flash 消息。为什么?我该如何解决这个问题?

路线
devise_for :users, :controllers => { :registrations => "registrations" }
注册控制器.rb
def create
    if verify_recaptcha
        super
        flash.delete(:recaptcha_error)
        else
        build_resource
        clean_up_passwords(resource)
        flash.delete(:recaptcha_error)
        flash[:alert] = "Typed keyword is not correct!"
        render :template => '/registrations/new' 
    end
end
查看闪光灯
<% flash.each do |name, msg| %>
  <div class="alert alert-<%= name == :notice ? "success" : "error" %>">
    <a class="close" data-dismiss="alert">×</a>
    <%= content_tag :div, msg, :id => "flash_#{name}" if msg.is_a?(String) %>
  </div>
<% end %>