LMMS master loses Carla instrument configuration when loading old project file

I have an old project file created in LMMS 1.2.2, which has a track whose instrument is a Carla rack with a loaded VST. If I load this project in the latest LMMS master, then the Carla rack loads, but many of the parameters of the VST instrument are set to 0.

The problem does not seem to occur if the project was saved with LMMS master instead of 1.2.2, then the instruments are loaded correctly.

#### Steps to reproduce

- Open LMMS 1.2.2 with a new project.
- Add a track with a Carla rack instrument.
- Load a VST plugin with Carla and set parameters as desired.
- Save the project and exit.
- Open LMMS master and open the previously saved project.
- Open the Carla rack GUI of the track in question.

#### Expected behavior

The VST parameters are preserved.

#### Actual behavior

The VST parameters are set to zero, including things like master volume, ADSR levels, filter cutoff etc. It depends on the instrument, but it happens with at least Dexed and TAL-U-No-LX.

#### Screenshot


#### Affected LMMS versions

3518d30

The bug does not occur in 1.3.0-alpha.1, so it must have been introduced at some point since.

Reproduce the migration from an LMMS 1.2.2 project to the affected master revision using a Carla rack and VST parameters. Compare the project-loading behavior between the affected revision and 1.3.0-alpha.1, then trace the loading path to identify why parameters become zero. Done means the saved VST parameters are preserved when opening the old project.

Written by the indexing model from the issue text.