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', '7ec4a59b5dd1b2f03968d98a38000c1f', '216.73.216.169', '1755543110', '1755543110', '/shop/index.php?cPath=9_5')

[XT SQL Error]