change test to slider for disk create

app/UI/Disk/Forms/UpdateForm.php

@@ -44,10 +44,10 @@ class UpdateForm extends BaseForm implements ClientArea
         $this->initFields();
         $this->loadDataToForm();
         $rangeField = $this->getField('additionalDiskSize');
-        $rangeField['minValue'] = parent::getFormData()['size'];
-        $rangeField['defaultValue'] = parent::getFormData()['size'];
+        $rangeField->minValue = parent::getFormData()['size'];
+        $rangeField->defaultValue = parent::getFormData()['size'];
         $this->reloadForm();
-        
+
         logModuleCall(
             'proxmoxCloud',
             __FUNCTION__,