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', '24mt173hanks2o6f3kku3ul424', '216.73.216.9', '1757808985', '1757808985', '/shop_content.php?XTCsid=adc8c520bddaa9e02a40df1e2a90f128&coID=2')

[XT SQL Error]