eth/protocols/eth,p2p/discover: remove unnecessary checks (#29590)

fix useless condition

eth/protocols/eth/handlers.go

@@ -190,7 +190,7 @@ func serviceContiguousBlockHeaderQuery(chain *core.BlockChain, query *GetBlockHe
 		return headers
 	}
 	{ // Last mode: deliver ancestors of H
-		for i := uint64(1); header != nil && i < count; i++ {
+		for i := uint64(1); i < count; i++ {
 			header = chain.GetHeaderByHash(header.ParentHash)
 			if header == nil {
 				break

p2p/discover/v4_udp.go

@@ -548,7 +548,7 @@ func (t *UDPv4) handlePacket(from *net.UDPAddr, buf []byte) error {
 	}
 	packet := t.wrapPacket(rawpacket)
 	fromID := fromKey.ID()
-	if err == nil && packet.preverify != nil {
+	if packet.preverify != nil {
 		err = packet.preverify(packet, from, fromID, fromKey)
 	}
 	t.log.Trace("<< "+packet.Name(), "id", fromID, "addr", from, "err", err)