1366 - Incorrect integer value: '' for column 'customer_id' at row 1

insert into whos_online (customer_id, full_name, session_id, ip_address, time_entry, time_last_click, last_page_url) values ('', 'Guest', 't19vp61udb6ffvu92sm9hi1vs1', '18.97.9.169', '1771363286', '1771363286', '/xtshop/password_double_opt.php')

[XT SQL Error]