TypeError if asking for what's playing on title with no artists

[declension]

Steps

• Have something playing / paused with no artist (or performer etc), e.g. internet streams
• Q: Ask Squeezebox what's playing

Expected

Nothing is playing or something similar

Actual

Oh Dear: TypeError: NoneType Object is not iterable

Traceback (most recent call last):
File "/var/task/handler.py", line 44, in lambda_handler
return sqa.handle(event, context)
File "/var/task/squeezealexa/main.py", line 60, in handle
return super(SqueezeAlexa, self).handle(event, context)
File "/var/task/squeezealexa/alexa/handlers.py", line 49, in handle
return self.on_intent(request, session)
File "/var/task/squeezealexa/main.py", line 85, in on_intent
return intent_handler(self, intent, session, pid=pid)
File "/var/task/squeezealexa/main.py", line 115, in now_playing
artist = human_join(people_from(details))
File "/var/task/squeezealexa/utils.py", line 37, in human_join
items = list(filter(None, items))
TypeError: 'NoneType' object is not iterable