Ruby on rails ActiveModel:：MassAssignmentSecurity:：UsersController#create中出错

我使用的是Rails 3.2.2，出现以下错误。下面的表单使用嵌套模型，我无法找到我已经尝试查找了几天的错误源

---

表单变量

class HomeController < ApplicationController

  def index
    @user = User.new
    @blog = @user.blogs.build
  end
end

<%= form_for @user do |f| %>
 <%= f.text_field :email, :class => 'textbox', :value => 'Email' %><br/><br/>
 <%= f.password_field :password, :class => 'textbox', :value => 'Password' %><br/><br/>
   <%= f.fields_for :blog do |b|%>
     <%= b.text_field :url, :class => 'textbox', :value => 'Blog URL' %></br></br>
   <% end %>

 <%= image_submit_tag("signup.png") %> <br/>
<% end %>

---

试着像这样在博客上添加一个s。应该是博客

<%= f.fields_for :blogs do |b|%>
     <%= b.text_field :url, :class => 'textbox', :value => 'Blog URL' %></br></br>
<% end %>

'文本框'，：value=>'博客URL'>

伙计，总是这些小事。有时，rails可能会处理这些错误消息！；）我知道。我很高兴能帮上忙。

class UsersController < ApplicationController

  def create
     @user = User.new(params[:user])   ############## << RUNTIME ERROR #############

     if @user.save 
       flash[:success] = "Welcome!"
       render 'user/success'             
     else
       render 'home/index'
     end
   end

class Blog < ActiveRecord::Base

   belongs_to :user
   attr_accessible :url, :type, :blog_id
   validates :url, :presence => true 

end

class User < ActiveRecord::Base

  has_many :blogs
  has_many :posts

  accepts_nested_attributes_for :blogs, :allow_destroy => true
  attr_accessible :email, :password, :user_id, :blogs_attributes 
end

  create_table "blogs", :force => true do |t|
    t.integer  "user_id"
    t.string   "url"
    t.string   "type"
    t.datetime "created_at", :null => false
    t.datetime "updated_at", :null => false
  end


  create_table "users", :force => true do |t|
    t.string   "email"
    t.datetime "created_at",      :null => false
    t.datetime "updated_at",      :null => false
    t.string   "password_digest"
    t.string   "remember_token"
  end

<%= f.fields_for :blogs do |b|%>
     <%= b.text_field :url, :class => 'textbox', :value => 'Blog URL' %></br></br>
<% end %>