phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '0' for key 'session_user_id'

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('685dd291f923f9bd482e18aaf866f0c4', -1, 1537833684, 1537833684, '3650537b', -4, 0, 0)

Line : 187
File : sessions.php