MyBB SQL Error

MyBB has experienced an internal SQL error and cannot continue.

SQL Error:
1062 - Duplicate entry '0' for key 'uid'
Query:
REPLACE INTO mybb_sessions SET `uid`='0',`sid`='acac0440ace265eaafaf2cedd3cafe8a',`time`='1498503906',`ip`='107.22.56.104',`location`='/forum/showthread.php?tid=62',`useragent`='CCBot/2.0 (http://commoncrawl.org/faq/)',`location1`='64',`location2`='62',`nopermission`='0'