allow empty enums

[tim2CF]

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In some cases in development process we should deal with empty enums. For example if actual business logic is not implemented yet, but we know for sure that there will be enum (which is empty atm). Or otherwise - we remove some values and enum become empty. To make development process smoother I want to support empty enums - in this case if business logic changes somehow, we don't need to modify enum-related code at all.