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', '1m08vlhin4k55fk8mi69t1tk40', '216.73.216.80', '1751315808', '1751315808', '/product_info.php?info=p14_65-drinking-cups-1-2-Liter.html&XTCsid=792dd2eece839333bab562194e3fb545')

[XT SQL Error]