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', 'c1b71763002d7c6b3f37d6f0ea2aa6a8', '3.91.249.156', '1711688019', '1711688019', '/index.php')

[XT SQL Error]