Handled the case when reading the crontab shows a "no crontab for www-data" which is usually returned for users that never had a cron job set (i.e. /var/spool/cron/crontabs/www-data doesn't exist). This is a bit different than an empty crontab (i.e. all jobs have been deleted), since /var/spool/cron/crontabs/www-data exists, but doesn't have any jobs.