Import of project from old version with solo'ed track- automation tracks don't unmute

[Monospace-V]

Bug Summary

When opening a project made in an older version of LMMS, wherein an instrument track has been solo'ed before saving, 1.3 alpha upon un-soloing the soloed tracks, automation tracks do not unmute. (Related, PR 5547, where the feature was added that enabled this behaviour.)
ie,
Soloing instrument track and save in 1.2, then re-opening in 1.3 alpha and un-soloing, keeps automation tracks muted.

Steps to reproduce

1. Create project in 1.2, make sure instrument track and automation track present in project.
2. Solo an instrument track and save the project file.
3. (Reopening the project file in 1.2 and un-soloing the instrument, the automation track is unmuted and becomes active.)
4. Opening the project file in 1.3 alpha, however, keeps automation tracks muted.

Expected behavior

Automation tracks should return to original state of unmuted upon un-solo'ing.

Actual behavior

Automation tracks remain muted.

Presumably this can be solved with version-checking of a project file, and the way unmuting a non-solo track works when a specific track is solo'ed, or how automation tracks can be re-muted after soloing an instrument track, but upon un-solo'ing they return to their original state.

Screenshot

File:
SoloTrack.zip

Affected LMMS versions

LMMS 1.3 alpha (by nature of bug)

[musikBear]

Great find!

[Spekular]

"mutedBeforeSolo" should be defaulting to false when not present (#5565), but maybe it's being saved as true somewhere, or #5547 has something to do with it?

[jphinspace]

I think I've been able to track this down - the block added here seems to be related #5547 (comment)

I'm not sure that block is really needed though, created a PR #6550 to remove it. Manual testing with this code fixes this issue and another I found where a muted automation track was being unmuted if it was soloed and then unsoloed.