BUG Suddenly 404 error

[Be-Mann]

For a short time now, our customers have not been able to enter roundcube, because the following error triggers a fatal error.

PHP8.0 is used
Roundcube 1.5-rc

PHP Fatal error: Uncaught TypeError: Unsupported operand types: string & bool in /var/www/web1/htdocs/webmail/plugins/rcguard/rcguard.php:404 Stack trace: #0 /var/www/web1/htdocs/webmail/plugins/rcguard/rcguard.php(53): rcguard->get_client_ip() #1 /var/www/web1/htdocs/webmail/program/lib/Roundcube/rcube_plugin_api.php(105): rcguard->init() #2 /var/www/web1/htdocs/webmail/program/include/rcmail.php(153): rcube_plugin_api->init() #3 /var/www/web1/htdocs/webmail/program/include/rcmail.php(86): rcmail->startup() #4 /var/www/web1/htdocs/webmail/index.php(43): rcmail::get_instance() #5 {main} thrown in /var/www/web1/htdocs/webmail/plugins/rcguard/rcguard.php on line 404