Display an optional message when date is null/invalid/undefined

[jramiresbrito]

The default behavior when the helper receives an invalid input is to return Invalid Date.

Optionally, from docs we can allow empty dates to be passed but it returns nothing:

{{moment-format '' allow-empty=true} {{!-- <nothing> --}}

But it could help a lot in my case if I could define an optional message. I'm currently doing this via a template helper:

export function formattedDate([date]) {
  return date ? moment(date).format('DD/MM/YY') : 'indisponível';
}

export default helper(formattedDate);

If possible, I'd like to eliminate this helper.