wrong MIDI for notes with two stems (and identical duration)

Version: 2.0.3+dfsg1-2+b1

Notes as the attachment shows have two MIDI on and off events each, easily leading to collision. In the keyboard model MuseScore uses, the volumes don’t accumulate anyway. CSV:

1421 5 73440 Note_on_c 4 68 50
1422 5 73440 Note_on_c 4 73 50
1950 6 73440 Note_on_c 4 53 50 ←
1951 6 73440 Note_on_c 4 61 50
1952 6 73440 Note_on_c 4 53 50 ←
1423 5 73679 Note_on_c 4 68 0
1424 5 73679 Note_on_c 4 73 0
1425 5 73680 Note_on_c 4 65 50
1426 5 73919 Note_on_c 4 65 0
1953 6 73919 Note_on_c 4 56 0
1954 6 73919 Note_on_c 4 53 0 ←
1955 6 73919 Note_on_c 4 53 0 ←

Note how 53 is both on’d and off’d twice each time. The integer-instead-of-boolean refcounting from my suggestion in the last paragraph of the description of https://musescore.org/en/node/240001 would likely fix this as well, though.