Empty fields returning None

[jtpavlock]

Going off the docs.

MediaFile attempts to always return a usable value (i.e., it never returns None or throws an exception when a tag is accessed). If a tag is not present, an empty and false value of the appropriate type – such as zero or the empty string – is returned.

>>> f = MediaFile('tests/resources/audio_files/empty.mp3')
>>> print(f.title)
None

Is this going against expected behavior or maybe the docs are out of date?

[sampsyo]

That's a good point—this did change in https://github.com/beetbox/beets/pull/660, and it also looks like the docstring for _safe_cast is out of date. Fields can now return None if the tag is missing altogether, which is useful for some clients.