phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '0' 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 ('ffb9624178244c039985b5681c09f8f7', -1, 1550658804, 1550658804, '345bb0fb', -4, 0, 0)

Line : 187
File : sessions.php