[MU4 Issue] Instrument change to unpitched instrument causes key signatures to appear on unpitched lines

[GabeS573]

Describe the bug
Using the Instrument Change text to change from a pitched to an unpitched instrument causes subsequent unpitched clefs to have a key signature.

To Reproduce
Steps to reproduce the behavior:

1. Create a score with any pitched instrument.
2. Add a key signature (other than C major/A minor).
3. Midway through the score, add an Instrument Change (from the text palette) and select an unpitched instrument (such as Drumset).
4. Notice that, on all subsequent lines, the unpitched clef still has the old key signature next to it. Additionally, these erroneous key signatures cannot be deleted (as far as I can tell).
   

Expected behavior
Lines with an unpitched clef should never show a key signature.

Platform information

• OS: Windows 11

[erinic04]

A workaround would be to add the atonal key signature locally to the staff when it changes

[GabeS573]

A workaround would be to add the atonal key signature locally to the staff when it changes

@erinic04 That workaround doesn't work because local key signatures can't be added to unpitched percussion parts (i.e. Ctrl+dragging any key signature onto the unpitched staff does nothing).

The unpitched staff doesn't honor global key signatures either, leading to problems like this: