Does not work on CentOS Stream 9

[ne-lgute]

NagiosBPI seems to work with CentOS Sream 8 (at least the nagiosbpi page comes up).
With CentOS Stream 9, the nagiosbpi page only shows the title and this stack trace is logged.

Stack trace:
#0 /var/www/html/nagiosbpi/BpGroup_class.php(594): BpGroup->determine_this_state()
#1 /var/www/html/nagiosbpi/functions/bpi_functions.php(100): BpGroup->drill_down()
#2 /var/www/html/nagiosbpi/index.php(68): bpi_init()
#3 {main}
  thrown in /var/www/html/nagiosbpi/BpGroup_class.php on line 803