Use default value instead of raising an error when encountering an infinite loop in formulas.
Use default value instead of raising an error when encountering an infinite loop in formulas.

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