[16.0] mrp_bom_version: old_versions is not displayed (although computed)

[diggy128]

Module

mrp_bom_version

Describe the bug

Even though _compute_old_versions runs and sets old_versions field, nothing is shown in the UI when creating a new BOM version.

To Reproduce

Affected versions: 16.0

Steps to reproduce the behavior:

1. Create a BOM
2. Set it active
3. Create a new version
4. Check Versions tab

Expected behavior
Versions table should be updated and show previous BOM versions.