B17519: Filepond downloadButton behaviour corrected if no parameter is given. refs #17519

extension/Classes/Core/AbstractBuildForm.php

@@ -3126,7 +3126,10 @@ abstract class AbstractBuildForm {
          // Check for upload type new or old and initialize json config for new upload type
          $jsonConfig = array();
          $preloadedFiles = '';
-         $formElement[FE_FILE_DOWNLOAD_BUTTON] = $formElement[FE_FILE_DOWNLOAD_BUTTON] ?? '';
+         $downloadButton = $formElement[FE_FILE_DOWNLOAD_BUTTON] ?? false;
+         if ($downloadButton) {
+             $downloadButton = substr($this->evaluate->parse($formElement[FE_FILE_DOWNLOAD_BUTTON]), 2);
+         }
          $jsonConfig[UPLOAD_MIME_TYPE_ACCEPT] = $formElement[FE_FILE_MIME_TYPE_ACCEPT] ?? null;
          $jsonConfig[UPLOAD_MAX_FILE_SIZE] = $arr[FE_FILE_MAX_FILE_SIZE] ?? null;
          $jsonConfig[UPLOAD_MULTI_UPLOAD] = false;
@@ -3141,7 +3144,7 @@ abstract class AbstractBuildForm {
          $jsonConfig[UPLOAD_ID] = 1;
          $jsonConfig[UPLOAD_GROUP_ID] = $groupId ?? 0;
          $jsonConfig[UPLOAD_DROP_BACKGROUND] = 'white';
-         $jsonConfig[UPLOAD_DOWNLOAD_BUTTON] = substr($this->evaluate->parse($formElement[FE_FILE_DOWNLOAD_BUTTON]), 2);
+         $jsonConfig[UPLOAD_DOWNLOAD_BUTTON] = $downloadButton;
          $jsonConfig[UPLOAD_TYPE_FORM] = true;
          $jsonConfig[UPLOAD_FORM_ID] = $formElement[FE_HTML_ID];
          $jsonConfig[UPLOAD_SIP_DOWNLOAD_KEY] = $sipDownloadKey;