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', '2pr4gcsdj52lcb15m1j2cu1ei0', '216.73.216.88', '1762844972', '1762844972', '/shop_content.php?XTCsid=1455d70b156c4853db961f68b595bbe7&coID=3')

[XT SQL Error]