Merge pull request #73 from mpociot/fix/php-8.4

Remove PHP 8.4 deprecation warning

src/Application.php

@@ -162,7 +162,7 @@ public function useContainer(
      *
      * @return int 0 if everything went fine, or an error code
      */
-    public function runCommand($command, OutputInterface $output = null)
+    public function runCommand($command, ?OutputInterface $output = null)
     {
         $input = new StringInput($command);