Return the next node after the end of this bucket, or 0 if 0 == last(), so the range to traverse to traverse all nodes in the bucket is always [ first(), end() )] regardless of whether the bucket is empty.
Return the next node after the end of this bucket, or 0 if 0 == last(), so the range to traverse to traverse all nodes in the bucket is always [ first(), end() )] regardless of whether the bucket is empty.