Eliminated warning

src/AntiCSRF/Base.php

@@ -23,9 +23,9 @@ class Base implements AntiCSRFInterface
     /** @SuppressWarnings(PHPMD.Superglobals) */
     public function match(): bool
     {
-        $request_token = $_REQUEST[self::CSRF_TOKEN_IDX];
+        $request_token = $_REQUEST[self::CSRF_TOKEN_IDX] ?? false;
 
-        if (!is_null($request_token) && \hash_equals($this->token, $request_token))
+        if ($request_token && \hash_equals($this->token, $request_token))
         {
             return !$this->expired();
         }