Potential Error - Mailing list pgsql-docs

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/12/tutorial-fk.html
Description:

Hello

Thank you for your great tutorial.

I wasn't able to compile the below without a 'not null' after the primary
key word:

https://www.postgresql.org/docs/current/tutorial-fk.html

Just flagging in case it needs to be updated.

Thanks,
Ashok