Non CDMA phones (e.g. unagi) report 'GenericFailure' error. I don't know about what other non-CDMA devices report so I recommend to add the checking for the  'GenericFailure' error case.

```javascript
      if (req.error.name === 'RequestNotSupported' ||
          req.error.name === 'GenericFailure') {
        document.getElementById('operator-roaming-preference').hidden = true;
      }
```
BTW, hiding the roaming selector in case this feature is not supported is a nice trick ;)