Cannot repair failed assessment job with `databricks labs ucx repair-run`

Repair run is broken, as it cannot repair a failed workflow:
```
$ databricks labs ucx repair-run --step assessment
12:14:25  INFO [databricks.sdk] Using Databricks CLI authentication
12:14:25  INFO [d.labs.ucx] Repair Running assessment Job
12:14:27 ERROR [d.l.ucx.repair-run] AttributeError: 'NoneType' object has no attribute 'value'
```