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', 'r2iuirn19butmpir9k17dl30l5', '216.73.216.113', '1752227098', '1752227098', '/xtshop/product_info.php?info=p422_.html')

[XT SQL Error]