associations missing record causes error


I have 2 models

class Product < ActiveRecord::Base
  belongs_to :supplier

class Supplier < ActiveRecord::Base
  has_many :products

It can happen that a product has record where the supplier_id = 0.
When in my views I list all products and one of the columns has the
product.supplier.description field. This fails because there is no
record where the supplier_id = 0.

The user must set the supplier_id later on in the process but I want
to show the word "UNKNOWN" in the supplier.description while the is stil zero.

I cannot make a record in the database with supplier_id = 0 :frowning:

any ideas ?