Fatal error: Uncaught Error: Interface 'Sabre\DAV\ICollection' not found in /home/malert/WebDAV/vendor/sabre/dav/lib/DAVACL/IPrincipalCollection.php:17 Stack trace: #0 {main} thrown in /home/malert/WebDAV/vendor/sabre/dav/lib/DAVACL/IPrincipalCollection.php on line 17