fix Use of uninitialized value warnings.

[rspier]

Some fields in @$author end up being undefined. Replace them with an empty string instead.

[rspier]

That makes sense.

MariaDB [mod]> select * from users where fullname is null;
<snip for privacy>
+-----------+---------+---------------------+-------+-----------------+----------+----------+-----------+----------+------------+------------+-----------+
5 rows in set (0.007 sec)

MariaDB [mod]> update users set fullname=""  where fullname is null;
Query OK, 5 rows affected (0.011 sec)
Rows matched: 5  Changed: 5  Warnings: 0

MariaDB [mod]> select * from users where fullname is null;
Empty set (0.007 sec)

[rspier]

cron-daily runs warning free now.