The Consul API can pass through `Value: null` which does not get cast to
a string by ember-data. This snowballs into problems with `atob` which
then tried to decode `null`.
There are 2 problems here.
1. `Value` should never be `null`
- I've added a removeNull function to shallowly loop though props and
remove properties that are `null`, for the moment this is only on
single KV JSON responses - therefore `Value` will never be `null`
which is the root of the problem
2. `atob` doesn't quite follow the `window.atob` API in that the
`window.atob` API casts everything down to a string first, therefore it
will try to decode `null` > `'null'` > `crazy unicode thing`.
- I've commented in a fix for this, but whilst this shouldn't be
causing anymore problems in our UI (now that `Value` is never `null`),
I'll uncomment it in another future release. Tests are already written
for it which more closely follow `window.atob` but skipped for now
(next commit)