Two notes:
The gvm-check-setup script isn’t maintained by Greenbone (anymore) but by the Kali packaging team. To request an improvement for the unary operator expected message for better / more graceful handling of this case it is suggested to report a new issue over at https://bugs.kali.org
Updating any port numbers in the PostgreSQL config files is strongly discouraged as this will leave an unmaintained / deprecated PostgreSQL 14 version behind and in use which doesn’t receive any (security) updates anymore. Furthermore there might be other issues due the usage of such mixed PostgreSQL versions installed.
Usually you should get some instructions how to “upgrade” your PostgreSQL 14 version to the most recent 15 while updating your packages / OS (at least on Debian this is the case) and the related info can be also found at:
/usr/share/doc/postgresql-14/README.Debian.gz
or:
/usr/share/doc/postgresql-15/README.Debian.gz
External resources like e.g. the following is also giving more info:
https://www.muehlencord.de/wordpress/2020/10/31/postgresql-pg_upgradecluster/
Requesting more / better handling / notification / recommendations from the OS side could be also done via requests to Kali / Debian.