* Update the busy intervals of all attendees, and merge the results
*/
private void updateBusyIntervals() {
Activity activity = getActivity();
if (activity != null) {
List<Attendee> attendees = activity.withConstraints().withAttendees();
for (Attendee attendee : attendees) {
String agent = attendee.getAgent();
if (attendee.getResponseStatus() != RESPONSE_STATUS.declined) {
updateBusyInterval(agent);
}