send_interval is set to NULL when sending mails to all members of a group

I meant it looks a lot like issue #399628: emails not being sent to new users because send_interval=NULL, but I was too obsessed with the formatting of the db row. Also that issue didn't get solved, so it didn't give a lot of help.

By resubmitting the form on "admin/messaging/notifications" it got better. The newly added rows have a send_interval of 0, so should be send on the next cron run.

The problem seems to be that notifications_user_setting() is called without a default value, thus making the default become NULL.
The piece of code that's causing the problem:

$queue = array(
    'uid' => $uid,
    'sid' => 0,
    'module' => 'notifications',
    'eid' => $event->eid,
    'send_interval' => notifications_user_setting('send_interval', $account), // <-- This line
    'send_method' => notifications_user_setting('send_method', $account),// <-- And this line
    'cron' => 1,
    'created' => time(),
    'conditions' => 0,
  );

I have no time to make a real patch atm, and not even to check if this is also a problem in the latest dev version.
I think notifications_send_intervals() should be used to get a valid default value, or 0 should be used as an easy default.

I did find some time to write a patch.
_notifications_subscription_defaults() in the notifications.module file seems to use 0 and '' as the default values, so I used the same values for this function in the notifications_lite module.

Oh and I made the patch on the 2.x dev version.