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 ('9ff9b348afceb0ab9ff1d8d85c2697c2', -1, 1539928473, 1539928473, '36e11a2c', 2, 0, 0)

Line : 187
File : sessions.php