Address integration and phpstan errors

Author: sivaram7

src/App/GenericException.php

@@ -19,7 +19,7 @@ class GenericException extends \Exception
     /**
      * @inheritDoc
      */
-    public function __construct(string $message, int $code = 0, Throwable $previous = null)
+    public function __construct(string $message, int $code = 0, Throwable | null $previous = null)
     {
         parent::__construct($message, $code, $previous);
     }

src/Test/Integration/Schema/ValidatorTest.php

@@ -53,7 +53,7 @@ protected function setUp(): void
     public function testValidate(
         string $key,
         $value,
-        ResultInterface $expected = null,
+        ResultInterface | null $expected = null,
         string $stage = StageConfigInterface::STAGE_DEPLOY
     ): void {
         $expected = $expected ?? new Success();