SQL-DATABASE ERROR

Database error in WoltLab Burning Board (2.3.6 pl2): Invalid SQL: CREATE TABLE bb1_em2016_vortag (userid int(5), punkte int(10), pos int(3) default NULL auto_increment, PRIMARY KEY (pos));
mysql error: All parts of a PRIMARY KEY must be NOT NULL; if you need NULL in a key, use UNIQUE instead
mysql error number: 1171
mysql version: 5.7.25
php version: 5.3.29
Date: 01.12.2021 @ 22:53
Script: /wbb2/em2016.php
Referer: