Header of the application not appering as per the condition in _header.html.erb

I am following ruby on rails tutorials by michael harlt. I completed my user authentication system and it also working fine but according to the code of my header file it is not supposed to show "Users" and "Accounts" link until and unless the user is logged in.But as soon as I navigate to the login page or sign up page it is showing both these links even if the user is not logged in.

I am not getting any error while launching app in my browser Here I am posting all the relevant files. Any help would be appreciated.Thanks in advance ! For any other information please let me know.

session_controller.rb

class SessionsController < ApplicationController

  def new
  end

  def create
    user = User.find_by_email(params[:session][:email].downcase)
    if user && user.authenticate(params[:session][:password])
      log_in user
      remember user
      redirect_to user
    else
      flash.now[:danger] = 'Invalid email/password combination'
      render 'new'
    end
  end

  def destroy
    log_out if logged_in?
    redirect_to home_path
  end
end

sessions_helper.rb

module SessionsHelper

  # Logs in the given user.
  def log_in(user)
    session[:user_id] = user.id
  end

  # Remembers a user in a persistent session.
  def remember(user)
    user.remember
    cookies.permanent.signed[:user_id] = user.id
    cookies.permanent[:remember_token] = user.remember_token
  end

  # Returns the user corresponding to the remember token cookie.
  def current_user
    if (user_id = session[:user_id])
      @current_user ||= User.find_by_id(user_id)
    elsif (user_id = cookies.signed[:user_id])
      user = User.find_by_id(user_id)
      if user && user.authenticated?(cookies[:remember_token])
        log_in user
        @current_user = user
      end
    end
  end

  # Returns true if the user is logged in, false otherwise.
  def logged_in?
    !current_user.nil?
  end

  # Forgets a persistant session
   def forget(user)
     user.forget
     cookies.delete(:user_id)
     cookies.delete(:remember_token)
   end

   # Log Out Current User
  def log_out
    session.delete(:user_id)
    @current_user = nil
  end
end

_header.html.erb

<header class="navbar navbar-fixed-top navbar-inverse">
  <div class="container">
    <%= link_to "sample app", home_path, id: "logo" %>
    <nav>
      <ul class="nav navbar-nav navbar-right">
        <li><%= link_to "Home", home_path %></li>
        <li><%= link_to "Help", help_path %></li>

        <% if logged_in? %>
          <li><%= link_to "Users", '#' %></li>
          <li class="dropdown">
            <a href="#" class="dropdown-toggle" data-toggle="dropdown">
              Account <b class="caret"></b>
            </a>
            <ul class="dropdown-menu">
              <li><%= link_to "Profile", current_user %></li>
              <li><%= link_to "Settings", '#' %></li>
              <li class="divider"></li>
              <li>
                <%= link_to "Log out", logout_path, method: "delete" %>
              </li>
            </ul>
          </li>
        <% else %>
          <li><%= link_to "Log in", login_path %></li>
        <% end %>
      </ul>
    </nav>
  </div>
</header>

user.rb

class User < ActiveRecord::Base
  attr_accessor :remember_token
  before_save { self.email = email.downcase }
  validates :name,  presence: true, length: { maximum: 50 }
  VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i
  validates :email, presence: true, length: { maximum: 255 },
                    format: { with: VALID_EMAIL_REGEX },
                    uniqueness: { case_sensitive: false }
  has_secure_password
  validates :password, length: { minimum: 6 }

  # Returns the hash digest of the given string.
  def User.digest(string)
    cost = BCrypt::Engine::MIN_COST
    BCrypt::Password.create(string, cost: cost)
  end

  # Returns a random token.
  def User.new_token
    SecureRandom.urlsafe_base64
  end

  # Remembers a user in the database for use in persistent sessions.
  def remember
    self.remember_token = User.new_token
    update_attribute(:remember_digest, User.digest(remember_token))
  end

  # Returns true if the given token matches the digest.
  def authenticated?(remember_token)
     return false if remember_digest.nil?
    BCrypt::Password.new(remember_digest).is_password?(remember_token)
  end

  def forget
    update_attribute(:remember_digest, nil) 
  end
end