Multi-stave instrument has multiple tracks

1. Open attached MSCZ (produced in 1.3).
2. 'Export...'.
3. Choose 'MIDI'.
4. 'Save'.
5. Open MIDI file.

Expected result: There is one track for the piano in the MIDI Import Panel.
Actual result: There are two tracks for the piano in the MIDI Import Panel.

Note: The produced MIDI is also attached.

Discussion: Is this a bug?

Using MuseScore 2.0 Nightly Build (b0f01b4) - Mac 10.7.5.