fix: explicit nullable types (#4)

Author: marmichalski

src/Name.php

@@ -19,7 +19,7 @@ class Name
      *
      * @param array|null $parts
      */
-    public function __construct(array $parts = null)
+    public function __construct(?array $parts = null)
     {
         if (null !== $parts) {
             $this->setParts($parts);

src/Part/LastnamePrefix.php

@@ -6,7 +6,7 @@ class LastnamePrefix extends Lastname
 {
     protected $normalized = '';
 
-    public function __construct(string $value, string $normalized = null)
+    public function __construct(string $value, ?string $normalized = null)
     {
         $this->normalized = $normalized ?? $value;
 

src/Part/PreNormalizedPart.php

@@ -6,7 +6,7 @@ abstract class PreNormalizedPart extends AbstractPart
 {
     protected $normalized = '';
 
-    public function __construct(string $value, string $normalized = null)
+    public function __construct(string $value, ?string $normalized = null)
     {
         $this->normalized = $normalized ?? $value;