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

### 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](https://github.com/LMMS/lmms/files/8213324/SoloTrack.zip)

#### Affected LMMS versions
LMMS 1.3 alpha (by nature of bug)

Start by reproducing the issue with the attached SoloTrack.zip, comparing the project in LMMS 1.2 and 1.3 alpha after un-soloing the instrument track. Trace project-version handling and the solo/mute behavior for instrument and automation tracks. Done means automation tracks restore their original unmuted state after un-soloing.

Written by the indexing model from the issue text.