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', 's40902eu0mam1gj9c8eobs2f62', '216.73.216.185', '1752882727', '1752882727', '/popup_content.php?coID=1&XTCsid=81fba26e1f006e30d12d9ee4d58a4030')

[XT SQL Error]