Manual synchronization of CiviCRM memberships and Drupal roles gives error

Hello.

I am just starting to get memberships and roles sorted out in my CiviCRM. When I go to Home » Administration » Configuration » CiviCRM » CiviMember Roles Sync » Manually Synchronize and click the button, I get a popup saying "There was an error. CiviMember Memberships and Drupal Roles could not be synchronized." The Drupal log just says "unknown error".

On investigation, the problem appears in drupal/modules/civicrm_member_roles/civicrm_member_roles.module, line 530, in the method _civicrm_member_roles_sync():

  $contacts = CRM_Core_DAO::executeQuery($sql, $params);
  if ($contacts->N == 0) {
    watchdog('civicrm_member_roles',
      $errorMsg,
      $errorParams,
      WATCHDOG_ERROR
    );
    return FALSE;
  }

It is running the following sql:

SELECT DISTINCT uf.contact_id, m.end_date FROM civicrm_uf_match uf
      LEFT JOIN civicrm_membership m ON uf.contact_id = m.contact_id
      WHERE m.id IS NOT NULL AND m.membership_type_id IN (1)
      ORDER BY m.end_date DESC

which is returning zero rows. This is probably because I haven't got the necessary roles/contacts/etc set up, but it is a bit of an odd error.

Regards,

Carl