Compatability with php 8.4

Deprecate implicitly nullable parameter types
https://wiki.php.net/rfc/deprecate-implicitly-nullable-types

src/CrawlerDetect.php

@@ -76,7 +76,7 @@ class CrawlerDetect
     /**
      * Class constructor.
      */
-    public function __construct(array $headers = null, $userAgent = null)
+    public function __construct(?array $headers = null, $userAgent = null)
     {
         $this->crawlers = new Crawlers();
         $this->exclusions = new Exclusions();