fix implictit null parameter

Author: EmTeedee

src/JsFunctionsScanner.php

@@ -11,7 +11,7 @@ class JsFunctionsScanner implements FunctionsScannerInterface
     protected $validFunctions;
     protected $parser;
 
-    public function __construct(array $validFunctions = null)
+    public function __construct(?array $validFunctions = null)
     {
         $this->validFunctions = $validFunctions;
         $this->parser('latest');

src/JsNodeVisitor.php

@@ -18,7 +18,7 @@ class JsNodeVisitor
     protected $filename;
     protected $functions = [];
 
-    public function __construct(string $filename, array $validFunctions = null)
+    public function __construct(string $filename, ?array $validFunctions = null)
     {
         $this->filename = $filename;
         $this->validFunctions = $validFunctions;