PHP 8 compatibility issue

[MelissaWu-SS]

[Deprecated] urldecode(): Passing null to parameter #1 ($string) of type string is deprecated

Line 81 in /var/www/mysite/www/vendor/codecraft/silverstripe-pathfinder/src/Model/Store/RequestVarProgressStore.php

// Accept query variable from GET or POST
$this->encodedProgress = urldecode($request->requestVar($this->getProgressVarName()));