Fix 500 on job page when notifications are sending

Sending notifications don’t have an `updated_at`. This causes the time
formatting to throw a wobly, because it doesn’t expect `None`.

This commit changes the template to also look for the `created_at`,
which all notifications have.

app/templates/views/notifications.html

@@ -94,7 +94,7 @@
     {{ text_field(item.status|format_notification_status) }}
 
     {% call field(align='right') %}
-      {{ item.updated_at|format_datetime_short }}
+      {{ (item.updated_at or item.created_at)|format_datetime_short }}
     {% endcall %}
   {% endcall %}