phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' 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 ('62ddf1794898c6f9a5e55a1f29bd6d51', -1, 1545200707, 1545200707, '3693100c', 1, 0, 0)

Line : 187
File : sessions.php