As a user, I should be able to specify if a field is not printed on the packaging

[VaiTon]

On the website we use the hyphen (-) to tell that the value is not on the product. For example, it is really useful to tell that there is no fiber value printed on the packaging: in some case that does not mean there is no fiber, but only that the producer didn't print it. See https://github.com/openfoodfacts/openfoodfacts-server/issues/1938

Originally posted by @CharlesNepote in https://github.com/openfoodfacts/smooth-app/issues/2138#issuecomment-1149180607