statementInvalid error while using Rails 3 with mysql

I am getting the following error while trying to submit the data.

Error:

ActiveRecord::StatementInvalid in AdminsController#create_registration

NoMethodError: undefined method `name' for nil:NilClass: INSERT INTO `admins` (`created_at`, `email`, `password_hash`, `password_salt`, `picture`, `updated_at`, `user_name`) VALUES (?, ?, ?, ?, ?, ?, ?)
Rails.root: C:/Site/swargadwar_admin

Application Trace | Framework Trace | Full Trace
app/controllers/admins_controller.rb:4:in `create_registration'

I am explaing my codes below please check this and try to help me to resolve this error.

views/homes/index.html.erb

<div class="container">
    <div style="text-align:center;"><img src="/assets/admin.png" style="width:100px; height:120px; " /></div>
    <div class="text-div" style="text-align:center;">Swargadwar, Puri Municipality,govt of odisha</div>
            <section>               
                <div id="container_demo" >
                    <!-- hidden anchor to stop jump http://ift.tt/GTC0Ig  -->
                    <a class="hiddenanchor" id="toregister"></a>
                    <a class="hiddenanchor" id="tologin"></a>
                    <div id="wrapper">
                        <div id="login" class="animate form">
                            <form  action="mysuperscript.php" autocomplete="on"> 
                                <h1>Log in</h1> 
                                <p> 
                                    <label for="username" class="uname" data-icon="u" > Your email or username </label>
                                    <input id="username" name="username" required type="text" placeholder="myusername or mymail@mail.com"/>
                                </p>
                                <p> 
                                    <label for="password" class="youpasswd" data-icon="p"> Your password </label>
                                    <input id="password" name="password" required type="password" placeholder="eg. X8df!90EO" /> 
                                </p>
                                <p class="keeplogin"> 
                                    <input type="checkbox" name="loginkeeping" id="loginkeeping" value="loginkeeping" /> 
                                    <label for="loginkeeping">Keep me logged in</label>
                                </p>
                                <p class="login button"> 
                                    <input type="submit" value="Login" /> 
                                </p>
                                <p class="change_link">
                                    Not a member yet ?
                                    <a href="#toregister" class="to_register">Join us</a>
                                </p>
                            </form>
                        </div>

                        <div id="register" class="animate form">
                            <%= form_for :admin,:url => {:action => 'create_registration',:controller => "admins" } do |f| %>
                                <h1> Sign up </h1> 
                                <p> 
                                    <label for="usernamesignup" class="uname" data-icon="u">Your username</label>
                                    <%= f.text_field :user_name,placeholder:"mysuperusername690",:id => "usernamesignup" %>
                                </p>
                                <p> 
                                    <label for="emailsignup" class="youmail" data-icon="e" > Your email</label>
                                     <%= f.email_field :email,placeholder:"mysupermail@mail.com",:id => "emailsignup" %>
                                </p>
                                <p> 
                                    <label for="passwordsignup" class="youpasswd" data-icon="p">Your password </label>
                                    <%= f.password_field :password,placeholder:"eg. X8df!90EO",:id => "passwordsignup" %>
                                </p>
                                <p> 
                                    <label for="passwordsignup_confirm" class="youpasswd" data-icon="p">Please confirm your password </label>
                                    <%= f.password_field :password_confirmation,placeholder:"eg. X8df!90EO",:id => "passwordsignup" %>
                                </p>
                                <p>
                                     <label for="usernamesignup" class="uname" data-icon="u">Add Image</label>
                                     <%= f.file_field :picture %>
                                </p>
                                <p class="signin button">
                                <%= f.submit "Sign Up"%> 
                                </p>
                                <p class="change_link">  
                                    Already a member ?
                                    <a href="#tologin" class="to_register"> Go and log in </a>
                                </p>
                                <% end %>
                        </div>
                        <div class="error-div">
                                    <% if @admin.errors.any? %>
                                      <div id="error_explanation">
                                      <h2><%= pluralize(@admin.errors.count, "error") %> prohibited this post from being saved:</h2>

                                      <ul>
                                      <% @admin.errors.full_messages.each do |msg| %>
                                     <li><%= msg %></li>
                                     <% end %>
                                     </ul>
                                    </div>
                                  <% end %>
                               </div>
                    </div>
                </div>  
            </section>
        </div>

controller/admins_controller.rb

class AdminsController < ApplicationController
    def create_registration
        @admin=Admin.new(params[:admin])
        if @admin.save
            flash[:notice]="User has created successfully"
            flash[:color]="valid"
            redirect_to :action => "index" , :controller => 'homes'
        else
            flash[:alert]="User could not created"
            flash[:color]="invalid"
            render 'homes/index'
        end
    end
end

model/admin.rb

class Admin < ActiveRecord::Base
  attr_accessible :email, :password_hash, :password_salt, :picture, :user_name,:password_confirmation,:password
  attr_accessor :password
  before_save :encrypt_password
  EMAIL_REGEX = /\A[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\z/i
  validates :email, :presence => true, :uniqueness => true, :format => EMAIL_REGEX
  validates :user_name, :presence => true, :length => {:in => 3..10}
  validates :password, :confirmation => true
 validates_length_of :password, :in => 6..20, :on => :create
 def encrypt_password
    if password.present?
      self.password_salt = BCrypt::Engine.generate_salt
      self.password_hash = BCrypt::Engine.hash_secret(password, password_salt)
    end
  end
end

Actually error is showing at this line if @admin.save and I can not find where is name method here.Please try to resolve this error.