An employee is sending tickets into one of our helpdesk emails.

No one else seems to be having this issue, but he gets this bounce-back error:

Remote Server returned '554 5.3.0 < #5.3.0 x-unix; PHP Fatal error: Call to a member function isActive() on null in /var/www/osticket/upload/include/class.filter_action.php on line 454 PHP Stack trace: 
PHP 1. {main}() /var/www/osticket/upload/api/pipe.php:0 
PHP 2. PipeApiController::process() /var/www/osticket/upload/api/pipe.php:26 
PHP 3. TicketApiController->processEmail() /var/www/osticket/upload/include/api.tickets.php:223 
PHP 4. TicketApiController->createTicket() /var/www/osticket/upload/include/api.tickets.php:179 
PHP 5. Ticket::create() /var/www/osticket/upload/include/api.tickets.php:133 
PHP 6. Ticket::filterTicketData() /var/www/osticket/upload/include/class.ticket.php:3656 
PHP 7. TicketFilter->apply() /var/www/osticket/upload/include/class.ticket.php:3516 
PHP 8. Filter->apply() /var/www/osticket/upload/include/class.filter.php:764 
PHP 9. FilterAction->apply() /var/www/osticket/upload/include/class.filter.php:284 
PHP 10. FA_AssignTopic->apply() /var/www/osticket/upload/include/class.filter_action.php:98>'

Now I see towards the end there it references "Filter", but I honestly can't find a filter that would cause an issue with this user. Also why would the Filter error out? Wouldn't it either apply the rule or not?

Anyone else seen this error before?