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', '6fbgn8cik055cdqv8tk8jbhr72', '216.73.216.63', '1773757956', '1773757956', '/index.php?XTCsid=c9522ec8d7d3242bfbea3f87266d3e01')

[XT SQL Error]