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', '541f7017106dbe8482b4a0fb35df7905', '3.15.1.45', '1744901412', '1744901412', '/shop/product_info.php?info=p159_Anders-Kochen-von-Soeren-Anders.html')

[XT SQL Error]