Error when discharging

[Daedious]

When I try to discharge a member I get the following error on save:

TypeError: Argument 1 passed to IPS\perscom\Records\_AssignmentRecord::set_position() must be an instance of IPS\perscom\Units\CombatUnitPosition, null given, called in /home/fortheking/webapps/mainsite/forums/system/Patterns/ActiveRecord.php on line 372 (0)
#0 /home/fortheking/webapps/mainsite/forums/system/Patterns/ActiveRecord.php(372): IPS\perscom\Records\_AssignmentRecord->set_position(NULL)
#1 /home/fortheking/webapps/mainsite/forums/system/Node/Model.php(3094): IPS\Patterns\_ActiveRecord->__set('position', NULL)
#2 /home/fortheking/webapps/mainsite/forums/system/Node/Controller.php(413): IPS\Node\_Model->saveForm(Array)
#3 /home/fortheking/webapps/mainsite/forums/applications/perscom/modules/admin/records/assignment.php(0): IPS\Node\_Controller->form()
#4 /home/fortheking/webapps/mainsite/forums/system/Dispatcher/Controller.php(85): IPS\perscom\modules\admin\records\_assignment->form()
#5 /home/fortheking/webapps/mainsite/forums/system/Node/Controller.php(62): IPS\Dispatcher\_Controller->execute()
#6 /home/fortheking/webapps/mainsite/forums/applications/perscom/sources/Node/Controller.php(0): IPS\Node\_Controller->execute()
#7 /home/fortheking/webapps/mainsite/forums/applications/perscom/modules/admin/records/assignment.php(0): IPS\perscom\Node\_Controller->execute()
#8 /home/fortheking/webapps/mainsite/forums/system/Dispatcher/Dispatcher.php(152): IPS\perscom\modules\admin\records\_assignment->execute()
#9 /home/fortheking/webapps/mainsite/forums/admin/index.php(14): IPS\_Dispatcher->run()
#10 {main}