ethstats: avoid blocking chan when received invalid stats request

ethstats/ethstats.go

@@ -320,8 +320,13 @@ func (s *Service) readLoop(conn *websocket.Conn) {
 			request, ok := msg["emit"][1].(map[string]interface{})
 			if !ok {
 				log.Warn("Invalid stats history request", "msg", msg["emit"][1])
-				s.histCh <- nil
-				continue // Ethstats sometime sends invalid history requests, ignore those
+				select {
+				// treat it as an no indexes request in which we will return top ones block histories
+				case s.histCh <- nil:
+					continue
+				default:
+					continue
+				}
 			}
 			list, ok := request["list"].([]interface{})
 			if !ok {