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', '3pr2fep9g01mccbdsiqlt3m5h4', '216.73.216.185', '1752883009', '1752883009', '/index.php?XTCsid=5f051c452f1f75cd071b180063acc15b')

[XT SQL Error]