Unknown column 'a.contenttypeid' in 'where clause'

I encountered this error on import of data from vBulletin Version 3.8.6:

An AJAX HTTP error occurred. HTTP Result Code: 500 Debugging information follows. Path: /batch?id=258&op=do StatusText: Service unavailable (with message) ResponseText: PDOException: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'a.contenttypeid' in 'where clause': SELECT COUNT(*) AS expression FROM (SELECT 1 AS expression FROM {vbImport.attachment} a INNER JOIN {vbImport.attachmenttype} av ON a.extension = av.extension WHERE (a.contenttypeid IS NULL ) ) subquery; Array ( ) in vbimportapi_import() (line 985 of /var/www/html/sites/all/modules/vbtodrupal/vbimportapi.module).

It looks like it is caused by the vbtodrupal_query_vbtodrupal_attachment_alter function in vbtodrupal.module starting at line 434.

If I'm understanding the logic the following line is executed even if the contentid column does not exist:

$query->condition('a.contenttypeid', $contenttypeid);

I moved the line up into the if() and completed my import. Here is my updated version of this function:

/**
 * Implements hook_query_TAG_alter().
 */
function vbtodrupal_query_vbtodrupal_attachment_alter(QueryAlterableInterface $query) {
  $contenttypeid = &drupal_static(__FUNCTION__);
  if (!isset($contenttypeid)) {
    if (vbimportapi_import_db_column_exists('contentid', 'attachment')) {
      // vB 4 has a concept of content types.
      $contenttypeid = db_select('contenttype', 'ct')
        ->fields('ct', array('contenttypeid'))
        ->addTag('vbimport')
        ->condition('class', 'Post')
        ->execute()
        ->fetchField();
      $query->condition('a.contenttypeid', $contenttypeid);
    }
  }
}