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 ('6bc1505d29d2749b67896ed50bb0bda8', -1, 1539928415, 1539928415, '36e11a2c', -4, 0, 0)

Line : 187
File : sessions.php