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`='d3c9f8f7f99c3cc76d6c50601e6a6b50',`time`='1508496015',`ip`='54.224.197.86',`location`='/forum/showthread.php?tid=62',`useragent`='CCBot/2.0 (http://commoncrawl.org/faq/)',`location1`='64',`location2`='62',`nopermission`='0'