Fatal error: Uncaught Error: Interface 'Sabre\Xml\XmlSerializable' not found in /home/malert/WebDAV/vendor/sabre/dav/lib/DAV/Xml/Property/SupportedLock.php:21 Stack trace: #0 {main} thrown in /home/malert/WebDAV/vendor/sabre/dav/lib/DAV/Xml/Property/SupportedLock.php on line 21