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', '0ed98da620f20de3a1fec453b8de4428', '216.73.216.190', '1776277369', '1776277369', '/shop/product_info.php?info=p31_.html')

[XT SQL Error]