monitor fails to display details

Exception in phoenix log:

```
 File "/opt/birdhouse/src/pyramid-phoenix/phoenix/monitor/panels/__init__.py", line 35, in details
    return dict(job=job_details(request, job_id=job_id))
  File "/opt/birdhouse/src/pyramid-phoenix/phoenix/monitor/panels/__init__.py", line 21, in job_details
    if len(details['status_message']) > 250:
TypeError: object of type 'NoneType' has no len()
```