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', 'vt1mrquefc0sq6hj8kqu6ss3u7', '216.73.217.78', '1789840740', '1789840740', '/shop_content.php?XTCsid=d0fb6f95a363340d124d7dc76e615e44&coID=2')

[XT SQL Error]