p2p/discv5: minor code simplification (#18188)

* Update net.go

more simple

* Update net.go

p2p/discv5/net.go

@@ -567,12 +567,11 @@ loop:
 			net.ticketStore.searchLookupDone(res.target, res.nodes, func(n *Node, topic Topic) []byte {
 				if n.state != nil && n.state.canQuery {
 					return net.conn.send(n, topicQueryPacket, topicQuery{Topic: topic}) // TODO: set expiration
-				} else {
-					if n.state == unknown {
-						net.ping(n, n.addr())
-					}
-					return nil
 				}
+				if n.state == unknown {
+					net.ping(n, n.addr())
+				}
+				return nil				
 			})
 
 		case <-statsDump.C: