Decimal fields changed from zero to zero string marked as changed

Decimal fields with an old value of 0.0 that are changed to a string representation of zero ('0.0', '0.000', etc.) are included in changed_attributes.

    numeric_data = NumericData.new
    numeric_data.bank_balance = 0.0
    numeric_data.save!

    numeric_data.bank_balance = '0.0'
    numeric_data.changed_attributes # => {"bank_balance"=>#<BigDecimal:7f9f62ccefd0,'0.0',9(45)>}