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', 'kbrl7mgjckc7b0ah60om9kb9i4', '216.73.216.110', '1752971977', '1752971977', '/index.php?cat=c6_Foodstuffs.html&XTCsid=fae679bbce3acf80896a0577fc4b4b9a')

[XT SQL Error]