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 ('e8582b5d80a6d4d7940cf082f12ab7c2', -1, 1550803498, 1550803498, '22e5af81', 5, 0, 0)

Line : 172
File : sessions.php