Track Volume MIDI knob is reset to zero when song file is loaded

### Bug Summary

When MIDI controller knob is connected to a track's volume I can't control the volume on that track by using mouse. Which maybe an overlooked design, but the volume is reset to 0 when the song is loaded, or even when the default song is loaded.

#### Steps to reproduce
I suspect it happens on some MIDI hardware where the knobs are rotating 360 without abolute/relative number. But the tracks are being affected when they first load and read zero or assume zero. If you create lots of tracks and they take a moment to load you can see the volume level being on while it's loading and then all drop to 0 at once.

- Set a Volume control on a track to be controlled by a midi knob
(by right click on the volume graphic and pick Connect to controller...)
- Set an absolute knob on your MIDI controller and dial the volume to a value
- Save the test song and load it again
- Volume's at zero, and you can't pull it back to be audible with the mouse
- Especially bad when you have to reload LMMS to test sound and your song resets it to zero, which makes restart-testing frustrating

#### Expected behavior
The volume level should be saved with the song, and when loaded all volume levels should be the same as producer designed.

#### Actual behavior
When loading the volume is reset to 0 and can't be controlled even by mouse. No way to get original values

#### Affected LMMS versions
1.2.2

No source files or tests are named in the report. Reproduce the issue using the listed MIDI-controller and song-loading steps, then trace how track volume and controller connections are restored during song loading; done means saved track volumes remain audible and mouse control still works after reload.

Written by the indexing model from the issue text.