Add registration date and last active time as mass mail criteria

[Starpaul20]

From my list posted here; adds registration date and the time the user was last active as mass mail criteria.

[JN-Jones]

This doesn't work if you set the postnum to "0" (eg. send an email to users with 0 posts).

if($conditions[$search_field] && $conditions[$direction_field])

You need to add an isset instead of simply check them (0 is assumed as false)

[JN-Jones]

Now we have the exactly the opposite of it: the fields are always added: string(91) "u.allownotices=1 AND u.postnum>'0' AND u.regdate<'1380971039' AND u.lastactive<'1380971039'" (haven't selected anything). It would be better to use empty. In addition it would be possible to set the time fields to "0" which isn't really necessary.

[Starpaul20]

Okay, that should fix it

[JN-Jones]

Thanks for your Pull Request.

PS: This was your first PR that was merged without conflicts :P