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', 'u8ieurok7njpg72fhkjpua2420', '216.73.216.9', '1758140740', '1758140740', '/index.php?XTCsid=f31e6413a10f9b0bca585f648b3a21ac')

[XT SQL Error]