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', '8imtfui2qrd1s3jsa6t2eore61', '216.73.216.117', '1790038966', '1790038966', '/xtshop/product_info.php?info=p494_.html')

[XT SQL Error]