web interface fails to fully populate

Javascript console shows:
```js
TypeError: devList[parseInt(...)] is undefined[Learn More]
```
present in multiple versions.
Probably [sensorgnome.js](https://github.com/jbrzusto/sensorgnome/blob/rpi/master/public/javascripts/sensorgnome.js) has a race condition which doesn't show up in all network
situations.