Handling $query->joinWith called inside of other $query->joinWith with Closure

Handling $query->joinWith called inside of other $query->joinWith with Closure (called inside Closure). Ex.:

```php
$query->joinWith( [ 'rel1' => function($query) {
   $query->joinWith( [ 'rel2' => function($query) {
       // ...
   } ] );
} ] );
```