Update method signatures to accept nullable input (#590)

Co-authored-by: Deeka Wong <8337659+huangdijia@users.noreply.github.com>

src/Traits/ValidatesInput.php

@@ -49,7 +49,7 @@ protected function attributes(): array
      *
      * @throws ValidationException
      */
-    protected function setUpValidatesInput(InputInterface $input, OutputInterface $output): void
+    protected function setUpValidatesInput(?InputInterface $input, ?OutputInterface $output): void
     {
         if (empty($rules = $this->rules())) {
             return;