Typo in webform_file_download prevents users from downloading private files

Downloading private files form submissions doesn't work properly.

webform_file_download checks whether $file->sid is empty and then uses $row->sid to load the submission.

Below code fixes this problem:

@@ -1003,7 +1003,7 @@ function webform_file_download($uri) {
if ($row) {
$file = file_load($row->fid);
}
- if (!empty($file->sid)) {
+ if (!empty($row->sid)) {
$submissions = webform_get_submissions(array('sid' => $row->sid));
$submission = reset($submissions);
}