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 ('a6c1eb5d6b52fce4662331f15794b8f3', -1, 1537897883, 1537897883, '36a6cb11', 64, 0, 0)

Line : 187
File : sessions.php