fixes array index issue

src/Form/ConfirmCsvExportForm.php

@@ -28,6 +28,7 @@ class ConfirmCsvExportForm extends EntityConfirmFormBase {
     $survey = $this->entity->id();
     $options = [
       'survey' => $survey,
+      'export_type' => 'csv',
       'sent_to_bq' => FALSE,
       'truncate' => FALSE,
       'batch_size' => 75,