ACFIntegration: Empty Datepickerfield returns "" instead of null

[rubas]

Problem

If you have an empty DatePicker field in ACF:

• $post->raw_meta('empty_date_field') returns null
• $post->meta('empty_date_field') returns ""

Solution

We return null, if !$value instead of $value.

Alternative

Maybe it's more in the spirit of the ACF to return false, but 😕
null though allows you to chain easily $post->meta('empty_date_field')?->format('d. F Y').

[coveralls]

coverage: 87.937%. remained the same
when pulling 334fdd6 on rubas:patch-2
into 02ba68e on timber:2.x.

[gchtr]

A note for when we look at this more closely:

We made a change in #2904 to not change return values in meta to null, because it could lead to problems if we over-optimize. The failing tests were on of these problems.

It could very well be that with the change in #2904, the result for raw_meta() and meta() doesn’t look different for date fields.