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', 'gca1ejhsdv2p7urgb4bftoq5l3', '216.73.217.92', '1781008398', '1781008398', '/xtshop/advanced_search.php')

[XT SQL Error]