[BUGFIX] PhpStan Variable $parameters in empty() always exists and is…

… not falsy

Fixes PhpStan-issue:

```
------ -----------------------------------------------------------------
  Line   Classes/System/Url/UrlHelper.php
 ------ -----------------------------------------------------------------
  52     Variable $parameters in empty() always exists and is not falsy.
 ------ -----------------------------------------------------------------
```

Classes/System/Url/UrlHelper.php

@@ -48,10 +48,7 @@ public function withQueryParameter(string $parameterName, $value): UrlHelper
     {
         parse_str($this->query, $parameters);
         $parameters[$parameterName] = $value;
-        $query = '';
-        if (!empty($parameters)) {
-            $query = http_build_query($parameters);
-        }
+        $query = http_build_query($parameters);
         $query = $this->sanitizeQuery($query);
         $clonedObject = clone $this;
         $clonedObject->query = $query;