phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' 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 ('48bb987851f4ae5a63e02fd6a8167e13', -1, 1556236786, 1556236786, '36eb04c4', 21, 0, 0)

Line : 187
File : sessions.php