[ticket/12331] Fix SQL error when inserting a new entry to profile field...

... data

There was a `Field 'pf_phpbb_interests' doesn't have a default value` error,
because we didn't specify values for the disabled fields.
We can not disable the `sql_return_on_error()` thou, because it otherwise we run
into `Duplicate entry '2' for key 'PRIMARY'` errors when the user submits the
form again but didn't change any values.

http://tracker.phpbb.com/browse/PHPBB3-12331