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 ('c0979e93e91a5c3e6e3b40df2e5da5f9', -1, 1539607552, 1539607552, '36c637a7', -4, 0, 0)

Line : 187
File : sessions.php