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', '0en8vk2oebuh527u7cs5l5t083', '216.73.216.178', '1768565834', '1768565834', '/shop_content.php?XTCsid=ea749d82d78692dfdcc9ae5e35913621&coID=2')

[XT SQL Error]