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', '95g197mb6p68q4ej3tioa8agk0', '18.97.14.87', '1786721368', '1786721368', '/xtshop/index.php')

[XT SQL Error]