Bug with installer/interface
When installing with the newer and stricter Mysql servers (It wasn't my choice or I would have used the one specified) the installer file sets the options for websites, such as SSL, ssi, cgi, etc, as type enum('y','n') but the code in sites/web_vhost_subdomain_edit.php uses '-' instead of 'n' and tries to pass that to the database.
Modern Mysql and it's replacements, now reject that with an error instead of defaulting to the 'default' value.
Simple fix is to convert the '-' to 'n' in sites/web_vhost_subdomain_edit.php and in sites/web_domain_edit.php.
Patch file available on request.