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', 'vv8hpjfqce55nmlaev999hl7s4', '3.85.92.139', '1561469857', '1561469857', '/shop_content.php/coID/9/product/DIR-System')

[XT SQL Error]