musicxml2ly: Fix handling of minor chords
In particular, avoid incorrect output of power chords.
Patch taken from http://codereview.appspot.com/305700043 and adapted to current code base.
Fixes issue #4980 (closed).
In particular, avoid incorrect output of power chords.
Patch taken from http://codereview.appspot.com/305700043 and adapted to current code base.
Fixes issue #4980 (closed).