fix: Update transaction validation logic in ethclient

- Declare zeroAddress as a constant

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

@@ -164,10 +164,10 @@ func (ec *Client) getBlock(ctx context.Context, method string, args ...interface
 	}
 	if head.TxHash == types.EmptyTxsHash && len(body.Transactions) > 0 {
 		// If there is only one transaction in the block and the header's txHash is `EmptyTxsHash`,
-		// it indicates a sync transaction. No error handling is required in this case.
+		// it indicates a state-sync transaction. No error handling is required in this case.
 		tx := body.Transactions[0]
-		zeroAddress := common.HexToAddress("0x0000000000000000000000000000000000000000")
-		if (tx.From != nil && *tx.From != zeroAddress) || (tx.tx.To() != nil && *tx.tx.To() != zeroAddress) {
+		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")
 		}
 	}