sweep: fix handlePendingSweepsReq linter issue

Turns out the param was never used, we now fix it by sending the
response in the method and also catch the quit channel.

sweep/sweeper.go

@@ -672,7 +672,7 @@ func (s *UtxoSweeper) collector(blockEpochs <-chan *chainntnfs.BlockEpoch) {
 		// A new external request has been received to retrieve all of
 		// the inputs we're currently attempting to sweep.
 		case req := <-s.pendingSweepsReqs:
-			req.respChan <- s.handlePendingSweepsReq(req)
+			s.handlePendingSweepsReq(req)
 
 		// A new external request has been received to bump the fee rate
 		// of a given input.
@@ -1058,6 +1058,13 @@ func (s *UtxoSweeper) handlePendingSweepsReq(
 		}
 	}
 
+	select {
+	case req.respChan <- resps:
+	case <-s.quit:
+		log.Debug("Skipped sending pending sweep response due to " +
+			"UtxoSweeper shutting down")
+	}
+
 	return resps
 }