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', '93899f6a135d3a71f71fcc1df1bcf6e1', '216.73.217.75', '1789292430', '1789292430', '/shop/index.php?XTCsid=041c8fc0413f2441df67fe52a6815a15&cPath=3')

[XT SQL Error]