I have discovered two bugs that you can see demonstrated in the attached video.
Bug #1: Deleting multiple divisions at once jumps the tree view all the way to the top.
Steps to reproduce:
1. Open a SoundFont with a lot of instruments and presets (such as a GM bank).
2. Scroll down the tree view to find an instrument or preset with many divisions.
3. Click on a division, then shift-click another division to select multiple divisions.
4. Press the delete key (or right-click -> delete).
Result: the tree view jumps all the way to the top.
Expected result: the tree view should remain at the current instrument/preset.
Bug #2: After changing division sort order, deleted divisions appear as "..."
Steps to reproduce:
1. Open a SoundFont
2. In settings, change the division sort order. It doesn't seem to matter which option is selected, but I typically choose "none".
3. Expand an instrument or preset in the tree view and delete one or more of its divisions.
Result: the division name is replaced with "..." and remains in the tree view.
Expected result: the division should have been deleted and its space in the tree view eliminated.
I am running Polyphone 2.0 compiled in KDE neon 5.14 (based on Ubuntu 18.04).
