マイクロポスト検索を導入したいが、NoMethodError: undefined method `activated?' for nil:NilClassと出てしまう。

前提・実現したいこと

railsチュートリアルを終えて、この方の記事を参考にして、マイクロポスト検索を導入しようとしているのですが、下記のエラーメッセージが現れて、導入できません・

発生している問題・エラーメッセージ

NoMethodError: undefined method `activated?' for nil:NilClass

該当のソースコード

Ruby
1class UsersController < ApplicationController
2  before_action :logged_in_user, only: [:index,  :edit,
3                                        :update, :destroy,
4                                        :following, :followers]
5  before_action :correct_user,   only: [:edit, :update]
6  before_action :admin_user,     only: :destroy
7
8  def index
9    if params[:q] && params[:q].reject { |key, value| value.blank? }.present?
10      @q = User.ransack(search_params, activated_true: true)
11      @title = "Search Result"
12    else
13      @q = User.ransack(activated_true: true)
14      @title = "All users"
15    end
16    @users = @q.result.paginate(page: params[:page])
17  end
18
19  def show
20    redirect_to root_url and return unless @user.activated?
21    if params[:q] && params[:q].reject { |key, value| value.blank? }.present?
22      @q = @user.microposts.ransack(microposts_search_params)
23      @microposts = @q.result.paginate(page: params[:page])
24    else
25      @q = Micropost.none.ransack
26      @microposts = @user.microposts.paginate(page: params[:page])
27    end
28    @url = user_path(@user)
29  end
30
31  def new
32    @user = User.new
33    # => form_for @user
34  end
35
36  def create
37    @user = User.new(user_params)
38    if @user.save 
39      @user.send_activation_email
40      flash[:info] = "Please check your email to activate your account."
41      redirect_to root_url
42    else
43      render 'new'
44    end
45  end
46
47  def edit
48    @user = User.find(params[:id])
49  end
50
51  def update
52    @user = User.find(params[:id])
53    if @user.update_attributes(user_params)
54      # Success
55      flash[:success] = "Profile updated"
56      redirect_to @user
57    else
58      # Failure
59      # => @user.errors.full_messages()
60      render 'edit'
61    end
62  end
63
64  def destroy
65    User.find(params[:id]).destroy
66    flash[:success] = "User deleted"
67    redirect_to users_url
68  end
69
70  def following
71    @title = "Following"
72    @user  = User.find(params[:id])
73    @users = @user.following.paginate(page: params[:page])
74    render 'show_follow'
75  end
76
77  def followers
78    @title = "Followers"
79    @user  = User.find(params[:id])
80    @users = @user.followers.paginate(page: params[:page])
81    render 'show_follow'
82  end
83
84  private
85  
86    def search_params
87      params.require(:q).permit(:name_cont)
88    end
89
90    def user_params
91      params.require(:user).permit(
92        :name, :email, :password,
93        :password_confirmation)
94    end
95
96    def correct_user
97      @user = User.find(params[:id])
98      redirect_to(root_url) unless current_user?(@user)
99    end
100
101    def admin_user
102      redirect_to(root_url) unless current_user.admin?
103    end
104end