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 ('a3cbe0665b8da9826de31b8be7576b01', -1, 1540260207, 1540260207, '36e0f72a', -9, 0, 0)

Line : 187
File : sessions.php