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', 'clvj95dgp5mid30cmli9961og1', '216.73.216.113', '1752195021', '1752195021', '/xtshop/product_info.php?info=p395_.html')

[XT SQL Error]