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', 'op9cb124ip6mvjd4quds01o4l4', '216.73.217.69', '1790714851', '1790714851', '/xtshop/product_info.php?info=p1120_.html')

[XT SQL Error]