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', '8ri2k36us67pmdfvtat690hve7', '3.19.28.64', '1746772967', '1746772967', '/xtshop/product_info.php?info=p430_.html')

[XT SQL Error]