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', 'cgghruata9t0arqlb2vejrtah4', '216.73.216.94', '1751839573', '1751839573', '/xtshop/popup_content.php?coID=1')

[XT SQL Error]