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', 'd6q9pjcp5iinhdd49cko4db7k1', '216.73.216.49', '1752610243', '1752610243', '/xtshop/shop_content.php?coID=3')

[XT SQL Error]