SortControl: Still load a request's sort rule in getSort()

Icinga Cube does not even use `CompatController::createSortControl()`
or a custom override like Icinga Web Graphite Integration. Therefore,
unless it calls handleRequest(), we still need to load the sort rule
from the request in getSort() directly.

Should be easily reverted.

src/Control/SortControl.php

@@ -11,6 +11,7 @@
 use ipl\Orm\Query;
 use ipl\Stdlib\Str;
 use ipl\Web\Common\FormUid;
+use ipl\Web\Url;
 use ipl\Web\Widget\Icon;
 use Psr\Http\Message\ServerRequestInterface;
 
@@ -29,6 +30,13 @@ class SortControl extends Form
     /** @var string Name of the URL parameter which stores the sort column */
     protected $sortParam = self::DEFAULT_SORT_PARAM;
 
+    /**
+     * @var Url Request URL
+     * @deprecated Access {@see self::getRequest()} instead.
+     * @todo Remove once cube calls {@see self::handleRequest()}.
+     */
+    protected $url;
+
     /** @var array Possible sort columns as sort string-value pairs */
     private $columns;
 
@@ -41,12 +49,14 @@ class SortControl extends Form
      * Create a new sort control
      *
      * @param array $columns Possible sort columns
+     * @param Url $url Request URL
      *
      * @internal Use {@see self::create()} instead.
      */
-    private function __construct(array $columns)
+    private function __construct(array $columns, Url $url)
     {
         $this->setColumns($columns);
+        $this->url = $url;
     }
 
     /**
@@ -63,7 +73,7 @@ public static function create(array $options)
             $normalized[SortUtil::normalizeSortSpec($spec)] = $label;
         }
 
-        $self = new static($normalized);
+        $self = new static($normalized, Url::fromRequest());
 
         $self->on(self::ON_REQUEST, function (ServerRequestInterface $request) use ($self) {
             if ($self->getMethod() === 'POST' && $request->getMethod() === 'GET') {
@@ -158,7 +168,11 @@ public function setSortParam(string $sortParam): self
      */
     public function getSort(): ?string
     {
-        $sort = $this->getPopulatedValue($this->getSortParam(), $this->getDefault());
+        if ($this->getRequest() === null) {
+            $sort = $this->url->getParam($this->getSortParam(), $this->getDefault());
+        } else {
+            $sort = $this->getPopulatedValue($this->getSortParam(), $this->getDefault());
+        }
 
         if (! empty($sort)) {
             $columns = $this->getColumns();