Assigning user instances to tracks unlinks them from predicted

[talmo]

Bug description

Expected behaviour

Setting the track on a user instance that was created from a predicted instance causes predicted instances to re-appear.

Actual behaviour

Setting the track on a user instance that was created from a predicted instance should not cause predicted instances to appear.

Screenshots

User labeled instances created from predictions:

After assigning one instance to a track:

Instances panel shows all instances:

How to reproduce

1. Create a user instance from a predicted instance.
2. Assign the user instance to a track.
3. Predicted instance re-appears.