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