Assertion failure on adding instrument change in score with parts
This is certainly related to my parts playback patch so I'll probably work on this issue, this page is mostly to describe it.
Steps to reproduce:
1) Create a new score, for example, treble clef.
2) Create parts.
3) Drag an instrument change to any rest in master score.
Result: assertion failure in midimapping.cpp
Not sure whether this issue has any practical implications for scores playback but it would be better to handle such cases correctly.