Use correct css class in person.html

aleksis/apps/alsijil/templates/alsijil/class_register/person.html

@@ -74,7 +74,7 @@
         </li>
       {% empty %}
         <li class="collection-item avatar valign-wrapper">
-          <i class="material-icons left circle green white-text">check</i>
+          <i class="material-icons left materialize-circle green white-text">check</i>
           <span class="title">{% trans "There are no unexcused lessons." %}</span>
         </li>
       {% endfor %}