am 3674e1f7: am 854829de: am 4f84e648: am 6bf9b8ca: am 559a2420: Merge "MidiDevice: document that opens can return nulls" into mnc-dev

* commit '3674e1f701007d6f171da8b485b525b360e49d6d':
  MidiDevice: document that opens can return nulls