[BUGFIX] Make filter in receiver list work again for usergroups

For any reason, the first time when filtering after a group, everything works as expected. Nevertheless, the name of the select field changes from filter[usergroup] to filter[usergroup][__identity]. Even changing property to name did not help.

Classes/Controller/AbstractNewsletterController.php

@@ -98,6 +98,9 @@ protected function setFilter(): void
                 $filter
             );
         }
+        if (isset($filter['usergroup']['__identity'])) {
+            $filter['usergroup'] = $filter['usergroup']['__identity'];
+        }
         $clearFields = ['usergroup', 'configuration', 'category'];
         foreach ($clearFields as $clearField) {
             if (($filter[$clearField] ?? '0') === '0' || is_array($filter[$clearField])) {