Issue: Nullable transformable properties become empty instances

[ievgenii-syrotenko]

When using ClassTransformer\Hydrator::create(), nullable transformable properties (like DTOs) are incorrectly instantiated even if the input value is null.

Reproduction Steps

class ProductDTO
{
    public int $id;
    public string $name;
}

class DiscountDTO
{
    public string $code;
    public int $value;
}

class PurchaseDTO
{
    public ProductDTO $product;
    public ?DiscountDTO $discount;
    public float $cost;
}

$data = [
    'product' => ['id' => 1, 'name' => 'phone'],
    'discount' => null,
    'cost' => 10012.23,
];

$purchaseDTO = ClassTransformer\Hydrator::init()->create(PurchaseDTO::class, $data);
var_dump($purchaseDTO->discount);

✅ Expected

The discount property should be null.

❌ Actual

An empty DiscountDTO instance is created with uninitialized properties.

Root Cause

The bug was in PropertyTypeFactory::create() where the wrong flag was passed to TransformableType. Instead of $isNullable, it mistakenly passed $isScalar, so nullability wasn’t preserved.

✅ Fix

PR: #13 – Fix nullable transformable properties handling