Fix php 8.4 deprecations implicitly marking parameter as nullable is …

…deprecated

src/Config.php

@@ -67,10 +67,10 @@ public static function load($values, $parser = null, $string = false)
      * Loads a Config instance.
      *
      * @param  string|array    $values Filenames or string with configuration
-     * @param  ParserInterface $parser Configuration parser
+     * @param  ?ParserInterface $parser Configuration parser
      * @param  bool            $string Enable loading from string
      */
-    public function __construct($values, ParserInterface $parser = null, $string = false)
+    public function __construct($values, ?ParserInterface $parser = null, $string = false)
     {
         if ($string === true) {
             $this->loadFromString($values, $parser);
@@ -85,11 +85,11 @@ public function __construct($values, ParserInterface $parser = null, $string = f
      * Loads configuration from file.
      *
      * @param  string|array     $path   Filenames or directories with configuration
-     * @param  ParserInterface  $parser Configuration parser
+     * @param  ?ParserInterface $parser Configuration parser
      *
      * @throws EmptyDirectoryException If `$path` is an empty directory
      */
-    protected function loadFromFile($path, ParserInterface $parser = null)
+    protected function loadFromFile($path, ?ParserInterface $parser = null)
     {
         $paths      = $this->getValidPath($path);
         $this->data = [];
@@ -125,11 +125,11 @@ protected function loadFromFile($path, ParserInterface $parser = null)
      * Writes configuration to file.
      *
      * @param  string           $filename   Filename to save configuration to
-     * @param  WriterInterface  $writer Configuration writer
+     * @param  ?WriterInterface $writer Configuration writer
      *
      * @throws WriteException if the data could not be written to the file
      */
-    public function toFile($filename, WriterInterface $writer = null)
+    public function toFile($filename, ?WriterInterface $writer = null)
     {
         if ($writer === null) {
             // Get file information