Only have Imap enabled gives an error

[johan-smits]

I only have imap enabled because the calendar en contacts are synced with native card/caldav protocol.
The combined config file only has 1 imap backend, the rest is in comment.

I get these errors: PHP-Push-2/backend/combined/config.php:137 Use of undefined constant CALDAV_PORT - assumed 'CALDAV_PORT' (8)