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', 'hncgn7kv2k54aaqgo963jha576', '216.73.216.121', '1761779994', '1761779994', '/product_info.php?XTCsid=69a1e06b1d537d651878c63fe4ee3fec&info=p17_20-Tissue-Napkins.html')

[XT SQL Error]