rails画像アップロードでエラー

https://www.sejuku.net/blog/65175のサイトで画像アップロードを実装していましたがエラーが出ました。
少し前、似たような質問をしましたが、（https://teratail.com/questions/218253）解決できませんでした。

error
1ActionView::Template::Error (Nil location provided. Can't build URI.):
2    20:   <%= @ugblog.avatar_path %>
3    21: </p>
4    22: <p>
5    23:   <%= image_tag @ugblog.avatar_path.url %>
6    24: </p>
7    25:
8    26: <%= link_to '修正', edit_ugblog_path(@ugblog) %> |
9
10app/views/ugblogs/show.html.erb:23:in `_app_views_ugblogs_show_html_erb__349685954_118284500'

formhtmlerb
1<%= form_with(model: ugblog, local: true) do |form| %>
2  <% if ugblog.errors.any? %>
3    <div id="error_explanation">
4      <h2><%= pluralize(ugblog.errors.count, "error") %> prohibited this ugblog from being saved:</h2>
5
6      <ul>
7      <% ugblog.errors.full_messages.each do |message| %>
8        <li><%= message %></li>
9      <% end %>
10      </ul>
11    </div>
12  <% end %>
13
14  <div class="field">
15    <div><%= form.label :タイトル %></div>
16    <div><%= form.text_area :title, {cols:40} %></div>
17  </div>
18
19  <div class="field">
20    <div><%= form.label :サブタイトル %></div>
21    <div><%= form.text_area :subtitle, {cols:40, rows:5} %></div>
22  </div>
23
24  <div class="field">
25    <div><%= form.label :本文 %></div>
26    <div><%= form.text_area :Text, {cols:40, rows:10} %></div>
27  </div>
28  
29  <div class="field">
30    <div><%= form.label :写真 %></div>
31    <div><%= form.file_field :avatar_path, id: :ugblog_avatar_path %></div>
32  </div>
33
34  <div class="actions">
35    <%= form.submit  "投稿する" %>
36  </div>
37<% end %>

showhtmlerb
1<p id="notice"><%= notice %></p>
2
3<p>
4  <strong>タイトル:</strong>
5  <%= @ugblog.title %>
6</p>
7
8<p>
9  <strong>サブタイトル:</strong>
10  <%= @ugblog.subtitle %>
11</p>
12
13<p>
14  <strong>本文:</strong>
15  <%= @ugblog.Text %>
16</p>
17
18<p>
19  <strong>写真:</strong>
20  <%= @ugblog.avatar_path %>
21</p>
22<p>
23  <%= image_tag @ugblog.avatar_path.url %>
24</p>
25
26<%= link_to '修正', edit_ugblog_path(@ugblog) %> |
27<%= link_to 'トップページへ', ugblogs_path %>

indexhtmlerb
1<p id="notice"><%= notice %></p>
2
3<h2>みんなのブログ</h2>
4<table>
5<tr>
6<th><%= link_to '投稿する', new_ugblog_path %></th>
7<th><%= link_to 'ログアウト'.html_safe, destroy_user_session_path, method: :delete %></th>
8</tr>
9</table>
10<hr>
11<h2>投稿記事</h2>
12<table>
13  <thead>
14    <tr>
15      <th>タイトル</th>
16      <th>サブタイトル</th>
17      <th>本文</th>
18      <th colspan="3"></th>
19    </tr>
20  </thead>
21
22  <tbody>
23    <% @ugblogs.each do |ugblog| %>
24      <tr>
25        <td><%= ugblog.title.truncate(15) %></td>
26        <td><%= ugblog.subtitle.truncate(15) %></td>
27        <td><%= ugblog.Text.truncate(20) %></td>
28        <td><%= link_to '詳しく見る', ugblog %></td>
29        <td><%= link_to '編集', edit_ugblog_path(ugblog) %></td>
30        <td><a href="javascript:delData(<%= ugblog.id %>);">削除
31        </a></td>
32      </tr>
33    <% end %>
34  </tbody>
35</table>
36
37
38<br>
39
40
41<script>
42function delData(num){
43	if (confirm('このデータを削除しますか？')){
44		document.location = "/ugblogs/delete/" + num;
45	}
46	return false;
47}
48</script>
49
50<hr>

controller
1class UgblogsController < ApplicationController
2  layout 'ugblogs'
3  before_action :set_ugblog, only: [:show, :edit, :update, :destroy]
4
5  # GET /ugblogs
6  # GET /ugblogs.json
7  def index
8    @ugblogs = Ugblog.all.order('created_at desc').limit(3)
9  end
10
11  # GET /ugblogs/1
12  # GET /ugblogs/1.json
13  def show
14  end
15
16  # GET /ugblogs/new
17  def new
18    @ugblog = Ugblog.new
19  end
20
21  # GET /ugblogs/1/edit
22  def edit
23  end
24
25  # POST /ugblogs
26  # POST /ugblogs.json
27  def create
28    @ugblog = Ugblog.new(ugblog_params)
29
30    respond_to do |format|
31      if @ugblog.save
32        format.html { redirect_to @ugblog, notice: 'Ugblog was successfully created.' }
33        format.json { render :show, status: :created, location: @ugblog }
34      else
35        format.html { render :new }
36        format.json { render json: @ugblog.errors, status: :unprocessable_entity }
37      end
38    end
39  end
40
41  # PATCH/PUT /ugblogs/1
42  # PATCH/PUT /ugblogs/1.json
43  def update
44    respond_to do |format|
45      if @ugblog.update(ugblog_params)
46        format.html { redirect_to @ugblog, notice: 'Ugblog was successfully updated.' }
47        format.json { render :show, status: :ok, location: @ugblog }
48      else
49        format.html { render :edit }
50        format.json { render json: @ugblog.errors, status: :unprocessable_entity }
51      end
52    end
53  end
54
55  # DELETE /ugblogs/1
56  # DELETE /ugblogs/1.json
57  def destroy
58    @ugblog.destroy
59    respond_to do |format|
60      format.html { redirect_to ugblogs_url, notice: 'Ugblog was successfully destroyed.' }
61      format.json { head :no_content }
62    end
63  end
64
65  private
66    # Use callbacks to share common setup or constraints between actions.
67    def set_ugblog
68      @ugblog = Ugblog.find(params[:id])
69    end
70
71    # Never trust parameters from the scary internet, only allow the white list through.
72    def ugblog_params
73      params.require(:ugblog).permit(:title, :subtitle, :Text, :avatar_path)
74    end
75end
76