xmaker: remove invalid price error

pkg/strategy/xmaker/strategy.go

@@ -879,7 +879,7 @@ func (s *Strategy) updateQuote(ctx context.Context) error {
 	bestBid, bestAsk, hasPrice := s.sourceBook.BestBidAndAsk()
 	if !hasPrice {
 		s.logger.Warnf("no valid price, skip quoting")
-		return fmt.Errorf("no valid book price")
+		return nil
 	}
 
 	bestBidPrice := bestBid.Price