Fatal error: Uncaught Error: Class "Bitrix\Calendar\Core\Base\PropertyCollection" not found in D:\ktt\ttepla.com\public_html\bitrix\modules\calendar\lib\core\event\properties\attendeecollection.php:10 Stack trace: #0 {main} thrown in D:\ktt\ttepla.com\public_html\bitrix\modules\calendar\lib\core\event\properties\attendeecollection.php on line 10