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 ('28d20f75f0ca8097a8ab64bfc0113b5f', -1, 1545200608, 1545200608, '3693100c', 3, 0, 0)

Line : 187
File : sessions.php