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', '7ef6627991e43b81adaf0a73c8e3291f', '216.73.216.190', '1776277677', '1776277677', '/shop/index.php?cPath=9_18')

[XT SQL Error]