Conditional Relationship throws UnexpectedValueException('Unexpected resource relationship value.') when encoding

Example in Resource file's `relationships` method:
```php
return [
    $this->when($this->showAddress, $this->relation('address')),
];
```

Thrown in file `laravel-json-api/encoder-neomerx/src/Schema/Relationships.php` Line 103 as of `v1.0.0-alpha.3` because the `ConditionalList` iterator returns it as a `ConditionalField` instead of `JsonApiRelation`.