Fix PHP 8.4 tests compatibility

Author: SerafimArts

tests/CompatibilityTest.php

@@ -82,9 +82,9 @@ public function testSourceFactoryCompatibility(): void
 
         new class () implements SourceFactoryInterface {
             public function create($source): ReadableInterface {}
-            public function createFromString(string $content = '', string $name = null): ReadableInterface {}
+            public function createFromString(string $content = '', ?string $name = null): ReadableInterface {}
             public function createFromFile(string $filename): FileInterface {}
-            public function createFromStream($stream, string $name = null): ReadableInterface {}
+            public function createFromStream($stream, ?string $name = null): ReadableInterface {}
         };
     }
 
@@ -97,9 +97,9 @@ public function testSourceFactoryWithMixedCompatibility(): void
 
         new class () implements SourceFactoryInterface {
             public function create(mixed $source): ReadableInterface {}
-            public function createFromString(string $content = '', string $name = null): ReadableInterface {}
+            public function createFromString(string $content = '', ?string $name = null): ReadableInterface {}
             public function createFromFile(string $filename): FileInterface {}
-            public function createFromStream(mixed $stream, string $name = null): ReadableInterface {}
+            public function createFromStream(mixed $stream, ?string $name = null): ReadableInterface {}
         };
     }
 }