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 ('5cf371784cf6a60b2cc3e89e6f138466', -1, 1537898048, 1537898048, '36a6cb11', 1, 0, 0)

Line : 187
File : sessions.php