fix of critical bug: not handling of end of corpus in mwereader

libmwereader/mwereader.cpp

@@ -30,6 +30,8 @@ bool MWEReader::registered = TokenReader::register_path_reader<MWEReader>(
 	{
 		// TODO MWE stuff
 		Sentence::Ptr pSentence = inner_reader_->get_next_sentence();
+		if(pSentence == NULL)
+			return Sentence::Ptr();
 		Wccl::SentenceContext sc(pSentence);
 		return process_sentence(sc);