undefined method `errors' for nil:NilClass using RoR

I am getting the following error in my login form when i am trying to attempt by putting the wrong data which should usually shows the login failed message.

Error:

NoMethodError in Sessions#loginadmin

Showing C:/Site/swargadwar_admin/app/views/homes/index.html.erb where line #71 raised:

undefined method `errors' for nil:NilClass
Extracted source (around line #71):

68:                                 <% end %>
69:                         </div>
70:                         <div class="error-div">
71:                                     <% if @admin.errors.any? %>
72:                                       <div id="error_explanation">
73:                                       <h2><%= pluralize(@admin.errors.count, "error") %> prohibited this post from being saved:</h2>
74:   

Please check my codes below and let me to know where i am doing the mistake.

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>
            <% if !current_user %>              
                <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_for :admin,:url => {:action =>'loginadmin',:controller => 'sessions' } do |f| %>
                                <h1>Log in</h1> 
                                <p> 
                                    <label for="username" class="uname" data-icon="u" > Your email or username </label>
                                     <%= f.email_field :email,placeholder:"mysupermail@mail.com",:id => "username" %>
                                </p>
                                <p> 
                                    <label for="password" class="youpasswd" data-icon="p"> Your password </label>
                                     <%= f.password_field :password,placeholder:"eg. X8df!90EO",:id => "password" %>
                                </p>
                                <p class="keeplogin"> 
                                    <%= f.check_box :remember_me,:id => "loginkeeping" %>
                                                   <label for="loginkeeping">Keep me logged in</label>
                                 <%= link_to 'Forgetting password ?',admins_forget_path %>
                                                </p>
                                <p class="login button"> 
                                    <%= f.submit "Login" %>
                                </p>
                                <p class="change_link">
                                    Not a member yet ?
                                    <a href="#toregister" class="to_register">Join us</a>
                                </p>
                                <% end %>
                            </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> 
                 <% end %> 
            </section>
        </div>

controller/sessions_controller.rb

class SessionsController < ApplicationController
    def loginadmin
        @admin=Admin.authenticate(params[:admin][:email], params[:admin][:password])
        if @admin
            session[:user_id]=@admin.id
            cookies.signed[:user_id]=@admin.id
            params[:admin][:remember_me] == '1' ? remember(@admin) : forget(@admin)
            flash[:notice]="Login Successfull"
            flash[:color]="valid"
            redirect_to :action => "new", :controller => "admins"
        else
            flash[:notice]="Login Failed"
            flash[:color]="invalid"
            render 'homes/index'
        end
    end
    def removeuser
        session[:user_id] = nil
        cookies.delete :user_id
        flash[:notice]="user logged out successfully"
        flash[:color]="valid"
        redirect_to :action => 'index', :controller => 'homes'
    end
end

controller/homes_controller.rb

class HomesController < ApplicationController
    def index
        @admin=Admin.new
    end
end

Please help me to resolve this error.