Index: wp-includes/taxonomy.php
===================================================================
--- wp-includes/taxonomy.php	(revision 16378)
+++ wp-includes/taxonomy.php	(working copy)
@@ -586,7 +586,7 @@
 
 		$sql_single = get_objects_in_term( $query['terms'], $query['taxonomy'], $query );
 
-		if ( empty( $sql_single ) )
+		if ( empty( $sql_single ) || is_wp_error( $sql_single ) )
 			return ' AND 0 = 1';
 
 		$sql[] = $sql_single;