Minor fix.

libethereum/Client.cpp

@@ -285,7 +285,6 @@ LocalisedLogEntries Client::checkWatch(unsigned _watchId)
 #if ETH_DEBUG && 0
 		cdebug << "lastPoll updated to " << chrono::duration_cast<chrono::seconds>(chrono::system_clock::now().time_since_epoch()).count();
 #endif
-		auto& w = m_watches.at(_watchId);
 		std::swap(ret, w.changes);
 		w.lastPoll = chrono::system_clock::now();
 	} catch (...) {}