Tidify returns an empty DataFrame and no Error when it receives a dict with an empty Tuple.

Tidify cannot unroll this json object and does not return an error.
```
dat  = {'value': ()}
df = tidify(dat)
df
```

The same behavior happens when there are other KV pairs in the dictionary.
```
dat  = {'value': (), 'another_key': str}
df = tidify(dat)
df
```