Scrolling in parts dialog broken when multiple parts are selected

[avvvvve]

Issue type

UI bug

Bug description

When there are at least 17 parts listed in the parts dialog and more than one is selected (by shift or control/command clicking), scrolling in the list becomes visually glitchy.

Steps to reproduce

1. Create a score with at least 17 parts (either by adding 17 instruments or creating 17 parts)
2. Open Parts
3. Select at least two parts
4. Scroll down and scroll back up. See that scrolling is jumpy, blank rows occur, and parts appear unordered.

Screenshots/Screen recordings

parts-dialog-scroll-multiselect.mov

MuseScore Version

MuseScore version (64-bit): 4.1.1-232071203, revision: github-musescore-musescore-e4d1ddf

Regression

I don't know

Operating system

OS: macOS 13.4, Arch.: x86_64

Additional context

No response

[bkunda]

Confirmed still relevant in master