Cover art crashes program on track change

[tristangough]

When launching simple_print.py The metadata loads fine, but when the track changes the program crashes.

Unknown shairport-sync core (ssnc) code "pcst", with base64 data MjEzMDk0NDA5OQ==.

Looks like when the metadata.py file tries to write the cover art in line 98

file.write(self.songcoverart.binary). # this is not base64!

It references tempfile.py

return func(*args, **kwargs)
TypeError: a bytes-like object is required, not 'NoneType'

It seems like it's not recognizing newer Airplay codes, possibly since Airplay has been updated since you created this.