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', 'j0g05guqjget2l6v9o0bg6i5h0', '35.172.201.102', '1544490867', '1544490867', '/~liembergerphp/xtcommerce/index.php')

[XT SQL Error]