Attempted to load class "file" from the global namespace. Did you forget a "use" statement?

[math-GH]

Contao 4.9.2
Photoalbums 2.2.0

[2020-04-25 16:55:18] request.INFO: Matched route "contao_backend". {"route":"contao_backend","route_parameters":{"_route":"contao_backend","_scope":"backend","_token_check":true,"_controller":"Contao\\CoreBundle\\Controller\\BackendController::mainAction"},"request_uri":"domain.de/contao?do=photoalbums2&ref=cdmMiYto","method":"GET"} []

[2020-04-25 16:55:18] request.CRITICAL: Uncaught PHP Exception Symfony\Component\ErrorHandler\Error\ClassNotFoundError: "Attempted to load class "file" from the global namespace. Did you forget a "use" statement?" at /var/www/xxx/contao-4.9.x/vendor/craffft/contao-photoalbums2/system/modules/photoalbums2/classes/Pa2.php line 165 {"exception":"[object] (Symfony\\Component\\Debug\\Exception\\FatalThrowableError(code: 0): Attempted to load class \"file\" from the global namespace.\nDid you forget a \"use\" statement? at /var/www/xxx/contao-4.9.x/vendor/craffft/contao-photoalbums2/system/modules/photoalbums2/classes/Pa2.php:165)"} []

Betrifft die Zeile in https://github.com/Craffft/contao-photoalbums2/blob/master/system/modules/photoalbums2/classes/Pa2.php

Leider bin ich nicht fit genug in PHP, um den Fehler zu beheben.

[math-GH]

Die Lösung könnte das hier sein:
https://community.contao.org/de/showthread.php?77817-ben%C3%B6tige-PHP-Nachhilfe-Use-f%C3%BCr-file