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 ('50e5f1ecf38c8ce36488c6f07ae9f8e7', -1, 1542753593, 1542753593, '36a75f33', 7, 0, 0)

Line : 187
File : sessions.php