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 ('8b5372af8ffdc64b173a49a9fbdeb0b7', -1, 1540090047, 1540090047, '36c6d41e', -4, 0, 0)

Line : 187
File : sessions.php