NULL values in 'do_not_*' fields if blank in contact:create API

API calls to 'Contact' 'create' that have blank values for the 'do_not_email' (and similar) fields create a contact in the database with 'NULL' in those fields, eg:

$result = civicrm_api3('Contact', 'create', array(
'sequential' => 1,
'last_name' => "Foo",
'do_not_email' => "",
'contact_type' => "Individual",
));

Results in do_not_email being NULL

These people then do not receive mailings in CiviMail because the code expects to find a 1 or 0 in these fields, but not NULL.

Proposed solution

(Enforce these fields to be 1 or 0 in the API?)

Enforce 'NOT NULL' on the following fields in the civicrm_contact table:
do_not_email
do_not_phone
do_not_mail
do_not_sms
do_not_trade

As per the current configuration of the is_opt_out field.