Extra upload_N from upload_save:validate

upload_save:validate is outputing an extra 'upload_N' (i.e. 'upload_0' and 'upload_1' when there's only one file upload). This is countered by a check for is_numeric() in upload_save() (line 414 in current HEAD), but that shouldn't be necessary. The problem seems to originate in the following code in upload_nodeapi:validate (starting on line 250 in HEAD):

          $key = 'upload_'. count($_SESSION['file_uploads']);
          $file->source = $key;
          $file->list = 1;
          $file = file_save_upload($file);
          $node->files[$key] = $file;

Or, it could be the nonsensical file_check_upload('upload') on line 210 in HEAD. This caused the problems described in comment 51 and 53 of http://drupal.org/node/31354.