Grace notes don't transpose

To reproduce:
1. Create a blank piano and insert some notes
2. Add some grace notes to some of the notes
3. Select all of the notes, including the graces, and then transpose them using the down arrow, or Ctrl+Down/Up

Instead of being transposed down or up an octave, the grace notes stay on the same pitch.

A work-around is to select each grace note individually when transposing.