fix: Update transaction validation logic in ethclient

- Treat the block as valid if it contains a single sync transaction and the header's txHash is `EmptyTxsHash`.
- Consider a transaction as a sync transaction and skip error handling if either the `from` or `to` address is `zeroAddress`.

ethclient/ethclient.go

@@ -162,13 +162,15 @@ func (ec *Client) getBlock(ctx context.Context, method string, args ...interface
 	if head.UncleHash != types.EmptyUncleHash && len(body.UncleHashes) == 0 {
 		return nil, errors.New("server returned empty uncle list but block header indicates uncles")
 	}
-
 	if head.TxHash == types.EmptyTxsHash && len(body.Transactions) > 0 {
-		if !HasOnlySystemTransaction(body) {
+		// 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.
+		tx := body.Transactions[0]
+		zeroAddress := common.HexToAddress("0x0000000000000000000000000000000000000000")
+		if (tx.From != nil && *tx.From != zeroAddress) || (tx.tx.To() != nil && *tx.tx.To() != 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")
 	}
@@ -217,28 +219,6 @@ func (ec *Client) getBlock(ctx context.Context, method string, args ...interface
 		}), nil
 }
 
-// isZeroAddress checks if a given address is the zero address.
-func isZeroAddress(address *common.Address) bool {
-	return address != nil && address.String() == "0x0000000000000000000000000000000000000000"
-}
-
-// isSystemTransaction
-// A system transaction is identified when:
-// - The "from" and "to" addresses in the transaction are both zero addresses.
-func isSystemTransaction(tx rpcTransaction) bool {
-	return isZeroAddress(tx.From) && isZeroAddress(tx.tx.To())
-}
-
-// HasOnlySystemTransaction checks if a block contains only system transactions.
-func HasOnlySystemTransaction(block rpcBlock) bool {
-	for _, transaction := range block.Transactions {
-		if !isSystemTransaction(transaction) {
-			return false
-		}
-	}
-	return true
-}
-
 // HeaderByHash returns the block header with the given hash.
 func (ec *Client) HeaderByHash(ctx context.Context, hash common.Hash) (*types.Header, error) {
 	var head *types.Header