Steps to reproduce:

1. If you already have frontend set up, it's OK, just navigate manually to /ui/setup.php and stay in setup "Check of pre-requisites" page;
2. Disable currently active database extension (and restart web server to apply changes);
3. Reload the setup page.

Result:
Open log and see error:
Trying to access array offset on value of type null [setup.php:208 -> session_write_close() -> CCookieSession->write() -> CCookieSession->isAutologinEnabled() -> CConfigFile->{closure}() in include\classes\core\CCookieSession.php:194]

Expected:
No errors.