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', 'd9b7f1534cf7e2af99277fc2304dfec0', '216.73.216.190', '1776270881', '1776270881', '/shop/index.php?cPath=9_5')

[XT SQL Error]