An empty term-pipeline was wrongly implemented in SysTerrier. Now Terrier is passed the NoOp class specifically to setup a blank pipeline.
minor edits
__hack_n_hew() in Topics class is re-written to be idempotent. It could so far fix TREC SGML for an XML parser's consumption and now it can smoothly output a well-formed XML keeping it unchanged. This eases the use of TREC topics without worrying about their format.