Search builder creates "blank"/unnecessary rows for import/exxport mappings

Hi,
On one of our internal sites as well as on the 3.1.x demo and the 3.2 demo, I created a new Smart Group via the search builder using the following criteria:

Street address IS NOT NULL
City IS NOT NULL
State IS NOT NULL
Postal Code IS NOT NULL
Country IS NOT NULL

Here are the results of my testing:
On all sites the results were the same: the smart group was created along with "blank" import/export mappings. Attempts to delete the mappings result in the following error:
Sorry. A non-recoverable error has occurred.

DB Error: constraint violation

Database Error Code: Cannot delete or update a parent row: a foreign key constraint fails (`afscsandbox_civicrm/civicrm_saved_search`, CONSTRAINT `FK_civicrm_saved_search_mapping_id` FOREIGN KEY (`mapping_id`) REFERENCES `civicrm_mapping` (`id`)), 1451

To see the "blank" mapping, go to "Administer", "Configure", "Import/Export mappings". I realize why they can't be deleted but I wonder why they are being created in that "table".

Thanks,
Cynthia