phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'session_user_id'

INSERT INTO forum_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('6c454b5b6b4e2c2005d3a1f3d12c6c69', -1, 1540353252, 1540353252, '369ed0bd', 2, 0, 0)

Line : 187
File : sessions.php