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`='2ac6c61e1e744aa074d433feeb8eee82',`time`='1503148859',`ip`='54.80.30.49',`location`='/forum/showthread.php?tid=62',`useragent`='CCBot/2.0 (http://commoncrawl.org/faq/)',`location1`='64',`location2`='62',`nopermission`='0'