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', '1q3bp4fucb5vvci066nooj6nd2', '216.73.216.9', '1757919334', '1757919334', '/product_info.php?XTCsid=adc8c520bddaa9e02a40df1e2a90f128&info=p15_25-balloons.html')

[XT SQL Error]