Meta.active and meta.touched always undefined?

### Are you submitting a **bug report** or a **feature request**?

A bug report

### What is the current behavior?

Looks like the props `meta.active` and `meta.touched` of `FieldArrayRenderProps` are always `undefined`. To reproduce please open the sandbox and do anything with the fields.
https://codesandbox.io/s/react-final-form-field-arrays-forked-ebtzy0

### What is the expected behavior?

Not sure I'm getting it right from the docs but I would assume `meta.active` to be `true` if one of the fields in the array is active. Also, `meta.touched` could mean that at least one of the fields has been touched.
Alternatively, I'd expect these props to contain arrays of all the fields' corresponding meta values.
What I didn't expect is them being undefined all the time.

### Sandbox Link

https://codesandbox.io/s/react-final-form-field-arrays-forked-ebtzy0

### What's your environment?

```
"final-form": "4.20.1",
"final-form-arrays": "3.0.2",
"react": "16.8.6",
"react-dom": "16.8.6",
"react-final-form": "6.5.3",
"react-final-form-arrays": "3.1.4",
```

### Other information