Fix error on not authenticated users

app/templates/_base/navbar.html.j2

@@ -12,8 +12,12 @@
         <li><a href="{{ url_for('main.news') }}"><i class="material-icons left">email</i>News</a></li>
         <li>
           <a class="dropdown-trigger no-autoinit" data-target="nav-more-dropdown" href="#!" id="nav-more-dropdown-trigger">
+            {% if current_user.is_authenticated %}
             <img src="{{ url_for('users.user_avatar', user_id=current_user.id) }}" alt="avatar" class="circle left" style="height: 54px; padding: 10px 10px 0 0;">
             {{ current_user.username }} ({{ current_user.email }})
+            {% else %}
+            <i class="material-icons left">more_vert</i>
+            {% endif %}
           </a>
         </li>
       </ul>