accompanying course work: handle case end date is null

src/Bundle/ChillPersonBundle/Resources/views/AccompanyingCourseWork/list_by_accompanying_period.html.twig

@@ -28,6 +28,11 @@
                   <span>{{ 'accompanying_course_work.start_date'|trans }}</span>
                 </div>
               </li>
+              {% if w.endDate == null %}
+              <li>
+                <div class="label no-label"></div>
+              </li>
+              {% else %}
               <li class="{%if date(w.endDate) < date('now') %}completed{% endif %}">
                 <div class="date">
                   <span>{{ w.endDate|format_date('long') }}</span>
@@ -36,6 +41,7 @@
                   <span>{{ 'accompanying_course_work.end_date'|trans }}</span>
                 </div>
               </li>
+              {% endif %}
             </ul>
           </div>