fix: Update transaction validation logic in ethclient (#1435)

- Declare zeroAddress as a constant
- If there is only one transaction in the block and the header's txHash is `EmptyTxsHash`, it indicates a state-sync transaction. No error handling is required in this case.

ethclient/bor_ethclient.go

@@ -8,6 +8,10 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 )
 
+const (
+	zeroAddress = "0x0000000000000000000000000000000000000000"
+)
+
 // GetRootHash returns the merkle root of the block headers
 func (ec *Client) GetRootHash(ctx context.Context, startBlockNumber uint64, endBlockNumber uint64) (string, error) {
 	var rootHash string

ethclient/ethclient.go

@@ -163,7 +163,13 @@ func (ec *Client) getBlock(ctx context.Context, method string, args ...interface
 		return nil, errors.New("server returned empty uncle list but block header indicates uncles")
 	}
 	if head.TxHash == types.EmptyTxsHash && len(body.Transactions) > 0 {
-		return nil, errors.New("server returned non-empty transaction list but block header indicates no transactions")
+		// If there is only one transaction in the block and the header's txHash is `EmptyTxsHash`,
+		// it indicates a state-sync transaction. No error handling is required in this case.
+		tx := body.Transactions[0]
+		if (tx.From != nil && *tx.From != common.HexToAddress(zeroAddress)) ||
+			(tx.tx.To() != nil && *tx.tx.To() != common.HexToAddress(zeroAddress)) {
+			return nil, errors.New("server returned non-empty transaction list but block header indicates no transactions")
+		}
 	}
 	if head.TxHash != types.EmptyTxsHash && len(body.Transactions) == 0 {
 		return nil, errors.New("server returned empty transaction list but block header indicates transactions")