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', '690qh7vjquajfedb5ef73ee9u2', '18.212.83.37', '1558248464', '1558248464', '/shop/checkout_shipping.php?XTCsid=690qh7vjquajfedb5ef73ee9u2')

[XT SQL Error]