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 ('2dd756ba6f9950771aa9522a866f9a27', -1, 1534242391, 1534242391, '36516eba', -4, 0, 0)

Line : 187
File : sessions.php