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', '3l2hpmlh2k56sofvdhor26lkc1', '216.73.216.184', '1761914985', '1761914985', '/xtshop/shopping_cart.php')

[XT SQL Error]