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', 'qarroqqv9jug4uo95fejkqs157', '216.73.216.40', '1773634915', '1773634915', '/shop_content.php?XTCsid=903d490a11e72fb45b2507d2f3478040&coID=2')

[XT SQL Error]