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 ('e687fbf964b2aad31ab1764a8968f83f', -1, 1548239609, 1548239609, '36535d55', -4, 0, 0)

Line : 187
File : sessions.php