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', '4k78m5mce16s2da0re9agf8cj5', '216.73.216.25', '1782900841', '1782900841', '/xtshop/shop_content.php?coID=3')

[XT SQL Error]