Getting undefined method `[]' for nil:NilClass in Rails 3

I want to fetch text field value to my controller and do the search with database but i got the following error.

Error:

NoMethodError in HomesController#scan_hcsy

undefined method `[]' for nil:NilClass
Rails.root: C:/Site/swargadwar

Application Trace | Framework Trace | Full Trace
app/controllers/homes_controller.rb:38:in `scan_hcsy'

Please check my below code and try to resolve this error.

homes/hcsy_html.erb

<% if current_admin %>
<div class="header">
<div class="navbar-header">Swargadwar, Puri Municipality,govt of odisha</div>
<div class="nav navbar-top-links navbar-right">
<div class="image"></div>
</div>
<div class="name-div">

</div>
</div>
<div class="menu-div">
<div id="leftsidebtn">
 <ul>
   <li><a href="/homes/registration">Create User</a></li>
   <li><a href="/homes/hcsy">Scan Report</a></li>
   <li><a href="#">View and Payment Report</a>
    <ul>
    <li><a href="/homes/hcsy">HCSY</a></li>

   </ul>
  </li>

   <li><a href="#">Payment Validate</a></li>
   <li><a href="/sessions/removeadmin">Log Out</a></li>
 </ul>  
</div>
</div>
<div class="content-div">
    Logged in as:<%= current_admin.email %>
    <center><h1>HARICHANDRA SAHAYATA YOJANA SLIP</h1></center>
    <%= form_for :hcsy,:url => {:action =>'scan_hcsy' } do |f| %>
    <%= f.text_field :reciept,placeholder:"Get your scan code" %>
    <%= f.submit "search" %>
    <% end %>
</div>

<% end %>

controller/homes_controller.rb

class HomesController < ApplicationController
    def index

    end
    def registration
        @user=User.new
    end
    def usersave
        @admin=Admin.find(params[:id])
        @user=User.new(params[:user])
        @user.admin_id=@admin.id
        if @user.save
            flash[:notice]="User has created successfully"
            flash[:color]="valid"
            redirect_to :action => "index"
        else
            flash[:alert]="User could not created"
            flash[:color]="invalid"
            render 'registration'
        end
    end
    def hcsy_reg
        @hcsy=THcsy.new
    end
    def create_reg
        @hcsy=THcsy.new(params[:hcsy])
        if @hcsy.save
            flash[:notice]="Data has saved successfully"
            flash[:color]="valid"
            redirect_to :action => "index"
        else
            flash[:alert]="Data could not saved successfully"
            flash[:color]="invalid"
            render 'hcsy_reg'
        end
    end
    def scan_hcsy
        @hcsy=THcsy.find_by_Receipt_No(params[:hcsy][:receipt])
        if @hcsy
            flash[:notice]="Check the record"
            flash[:color]="valid"
            redirect_to :action => 'scanrecord'
        else
            flash[:alert]="Receipt number could not found"
            flash[:color]="invalid"
            render 'hcsy'
        end
    end
    def hcsy
        @hcsy=THcsy.new
    end
    def scan_record

    end
end

model/t_hcsy.rb

class THcsy < ActiveRecord::Base
  attr_accessible :Address, :Amount_Required, :B_Audio, :B_Thumb, :B_photo, :Beneficiary_Name, :Beneficiary_Rel_With_Decease, :Brahmin, :Business, :Created_by, :D_photo, :Date_Of_Required, :Deceased_Name, :Govt_Service, :HCSY_ID, :Land_Property, :Mobile_No, :Occupation, :Others, :PoliceStation, :Prev_Amount_Received, :Prev_Date_Recieved, :Prev_Receipt_No, :Receipt_No, :Recieved_Fund_Earlier, :Sdp_Id, :Updated_By,:BPL
  attr_accessor :receipt
end

Please help me.