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', '61r5acapvjegtm5ntpiqsf7ba4', '216.73.216.122', '1767814526', '1767814526', '/index.php?XTCsid=f54d8739844de79bbca5fee789c5b9c7')

[XT SQL Error]