String offset cast occurred

ErrorException in Terbilang.php line 93:
at HandleExceptions->handleError('8', 'String offset cast occurred', ....dan seterusnya
di coba di lumen 5.2 php 5.6 
sama di laravel 5.2 php 5.6 sama 7.0 sama

``` php
        $data = [
          'val' => $terbilang->make(10000),
           'lang' => 'id',
        ];
        return response()->json($data);
```
