Can we please all agree that a zero second message is NOT a voicemail?!? It does not warrant an email with a subject of "Voicemail message from (555) 555-1212". And you don't need to say "No transcription available." Of course there's no transcription, because the message is ZERO SECONDS LONG. No transcription is POSSIBLE. :-)
How about a subject of "Call (with no message) from (555)-1212" and a body of "No voicemail was left for this call."?
Similarly in the SmartLine app. A "No transcription available" item that when tapped leads to a 0-second "message" that can't be played is silly.