Don't fail when a test case has no input variable and no entity variable.
Don't fail when a test case has no input variable and no entity variable.

adrienpacifico/openfisca-core,openfisca/openfisca-core,benjello/openfisca-core,sgmap/openfisca-core,openfisca/openfisca-core,benjello/openfisca-core