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', 'mfpmvnp4rlt1ghm5bgsk8k6gn2', '216.73.216.9', '1758147531', '1758147531', '/product_info.php?XTCsid=ec23ca965190a8290c666be9c9947acd&info=p15_25-balloons.html')

[XT SQL Error]