`undefined` input with allow-empty=false renders current date

`{{moment-format undefined}}` renders the current date. This is unexpected and mildly confusing.

[ember-twiddle repro](https://ember-twiddle.com/d0655905d0c6617044b83786920141e6?openFiles=templates.application.hbs%2C)

Expected: Error.

Start with the linked Ember Twiddle repro and the `{{moment-format undefined}}` invocation in `templates.application.hbs`. Trace the `moment-format` entry point’s handling of `undefined` when `allow-empty=false`; done means it raises an error instead of rendering the current date, with a regression check if the project’s test structure identifies one.

Escrito por el modelo de indexación a partir del texto del issue.