adjust jinja2 templates to handle cases of no description

app/templates/events.html

@@ -20,7 +20,9 @@
                         </a>
                 </b>
                 <div>
+                    {% if event.tasks.description != None %}
                     <p>{{ event.tasks.description }}</p>
+                    {% endif %}
                 </div>
                 {% else %}
                     <div><p>(no task assigned... yet)</p></div>