Fix Customer delete issue

application/models/Customer.php

@@ -257,6 +257,7 @@ class Customer extends Person
 					'discount_type'		=> 0,
 					'package_id'		=> NULL,
 					'points'			=> NULL,
+					'sales_tax_code_id'	=> NULL,
 					'deleted'			=> 1
 				));
 		}