UNDO does not remove instrument from mixer
2.0.3 / 2.1 dev (4a34643) /Win 7.
1. Create a new score using the treble clef template.
2. Open the mixer.
3. Open the Instruments dialogue (I), and add (say) a drumset. Click OK.
4. UNDO (Ctrl + Z).
Expected result: The added drumset should disppear from the mixer.
Actual result: The drumset remains in the mixer.
5. Open the Instruments dialogue (I), then click OK.
Result: Now, the drumset is removed from the mixer.