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', 'qtcgln3vu46r33upvptk9ellf2', '54.162.109.90', '1495804018', '1495804018', '/product_info.php?info=p154_Cartoon-Tasse.html&cartoon=872')

[XT SQL Error]