Adding bar to part of multi-instrument score causes crash

1. Create score with two instruments (e.g. Piano and Clavichord).
2. 'Parts...'.
3. 'New'.
4. Tick an instrument.
5. 'OK'.
6. Click on the part.
7. 'Append Measure'.

Result: Crash.

Note: See attached log.

Using MuseScore 2.0 Nightly Build (0b96ea5) - Mac 10.7.5.