Regex.split gives RangeError when regex matches a zero length string

```elm
import Regex

re = Regex.fromString >> Maybe.withDefault Regex.never

Regex.split (re "\\b") "foo bar"
```

gives

> RangeError: Invalid array length
>    at Array.push (<anonymous>)
>    at _Regex_splitAtMost (<anonymous>:11:7)
>    at <anonymous>:1:1

Other examples:

- `Regex.split (re "d?") "foo bar"`
- `Regex.split (re "") "foo bar"`