$params['followup_activity_subject'] = $formValues['followup_activity_subject'];
$params['followup_date'] = $formValues['followup_date'];
$params['target_contact_id'] = $this->_contactIds;
- $params['followup_assignee_contact_id'] = explode(',', $formValues['followup_assignee_contact_id']);
+ $params['followup_assignee_contact_id'] = array_filter(explode(',', $formValues['followup_assignee_contact_id']));
$followupActivity = CRM_Activity_BAO_Activity::createFollowupActivity($activityId, $params);
$followupStatus = ts('A followup activity has been scheduled.');