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', '55ea5e9e1f45ad62e3cb357e9db35e9d', '216.73.216.42', '1763384106', '1763384106', '/shop/index.php?cat=c4_.html')

[XT SQL Error]