Uncaught mysqli_sql_exception in installer

[mattsches]

Tried to set up a fresh S9y installation with PHP 8.1 and the MySQLi backend - which failed due with

Fatal error: Uncaught mysqli_sql_exception: Table 'db.serendipity_authors' doesn't exist in /var/www/html/include/db/mysqli.inc.php on line 66

An exception seems to be expected in the installer, but only a PDOException, not a mysqli_sql_exception:

Serendipity/include/admin/installer.inc.php

Line 327 in d79ea27

} catch (PDOException $e) {

We should probably add another catch block

    } catch (mysqli_sql_exception $e) {
        $t = null;