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 ('a973f0b8f4d1021192ccd319ac2ddeda', -1, 1728965794, 1728965794, '23ad3012', -7, 0, 0)

Line : 172
File : sessions.php