Fix "Passing null to parameter #1 ($string) of type string is depreca…

…ted" on PHP 8.1

include/configclass.php

@@ -252,7 +252,7 @@ function __construct($name, $svnName, $serverRootURL, $group = null, $username =
 		$this->group = $group;
 		$this->username = $username;
 		$this->password = $password;
-		$this->clientRootURL = rtrim($clientRootURL, '/');
+		$this->clientRootURL = $clientRootURL !== null ? rtrim($clientRootURL, '/') : null;
 	}
 
 	// }}}