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', 'plph1m13tfki674sthgi06jfo3', '216.73.216.9', '1758148381', '1758148381', '/shop_content.php?XTCsid=5452c15f57f0ea9ce022f9dc9cfaa045&coID=4')

[XT SQL Error]