Bug when deleting a relationship type

While removing the relationship types that came built into the system, civicrm throws an error when I try to delete the "Household Member Of" relationship.What's weird is that I was able to delete the other 5 or 6 built in relationships just fine (i.e. sibling of, spouse of, employee of, etc).

Here's my backtrace:

backTrace

D:\Apache2\htdocs\drupal_website\modules\civicrm\CRM\Core\Error.php, backtrace, 147
, handle,
D:\Apache2\htdocs\drupal_website\modules\civicrm\packages\PEAR.php, call_user_func, 901
D:\Apache2\htdocs\drupal_website\modules\civicrm\packages\DB.php, PEAR_Error, 888
D:\Apache2\htdocs\drupal_website\modules\civicrm\packages\PEAR.php, DB_Error, 563
D:\Apache2\htdocs\drupal_website\modules\civicrm\packages\DB\common.php, raiseError, 1849
D:\Apache2\htdocs\drupal_website\modules\civicrm\packages\DB\mysqli.php, raiseError, 920
D:\Apache2\htdocs\drupal_website\modules\civicrm\packages\DB\mysqli.php, mysqliRaiseError, 395
D:\Apache2\htdocs\drupal_website\modules\civicrm\packages\DB\common.php, simpleQuery, 1162
D:\Apache2\htdocs\drupal_website\modules\civicrm\packages\DB\DataObject.php, query, 2344
D:\Apache2\htdocs\drupal_website\modules\civicrm\packages\DB\DataObject.php, _query, 1394
D:\Apache2\htdocs\drupal_website\modules\civicrm\CRM\Contact\BAO\RelationshipType.php, delete, 133
D:\Apache2\htdocs\drupal_website\modules\civicrm\CRM\Admin\Form\RelationshipType.php, del, 100
D:\Apache2\htdocs\drupal_website\modules\civicrm\CRM\Core\StateMachine.php, postProcess, 166
D:\Apache2\htdocs\drupal_website\modules\civicrm\CRM\Core\QuickForm\Action\Next.php, perform, 63
D:\Apache2\htdocs\drupal_website\modules\civicrm\packages\HTML\QuickForm\Controller.php, perform, 195
D:\Apache2\htdocs\drupal_website\modules\civicrm\packages\HTML\QuickForm\Page.php, handle, 95
D:\Apache2\htdocs\drupal_website\modules\civicrm\CRM\Core\Controller.php, handle, 213
D:\Apache2\htdocs\drupal_website\modules\civicrm\CRM\Core\Page\Basic.php, run, 307
D:\Apache2\htdocs\drupal_website\modules\civicrm\CRM\Core\Page\Basic.php, edit, 159
D:\Apache2\htdocs\drupal_website\modules\civicrm\CRM\Core\Invoke.php, run, 613
D:\Apache2\htdocs\drupal_website\modules\civicrm\CRM\Core\Invoke.php, admin, 86
D:\Apache2\htdocs\drupal_website\modules\civicrm\drupal\civicrm.module, invoke, 288
, civicrm_invoke,
D:\Apache2\htdocs\drupal_website\includes\menu.inc, call_user_func_array, 418
D:\Apache2\htdocs\drupal_website\index.php, menu_execute_active_handler, 15

Fatal error: Call to undefined function mysql_error() in D:\Apache2\htdocs\drupal_website\modules\civicrm\CRM\Core\Error.php on line 160