Check if chainId is not nil before constructing EIP155 signer

EIP155 signer does not perform chain ID validation and if chain ID is
nil, transaction is rejected by Ethereum client as not being EIP155
compliant. A simple chainId nil check was added in this commit. A
similar check is performed in the original go-ethereum code in
NewKeyedTransactorWithChainID function.

Author: pdyraga

tools/generators/ethlike/contract.go.tmpl

@@ -61,6 +61,9 @@ func New{{.Class}}(
 	// FIXME bumps beyond 1.9.25.
 	key := accountKey.PrivateKey
 	keyAddress := crypto.PubkeyToAddress(key.PublicKey)
+	if chainId == nil {
+		return nil, fmt.Errorf("no chain id specified")
+	}
 	transactorOptions := &bind.TransactOpts{
 		From: keyAddress,
 		Signer: func(_ types.Signer, address common.Address, tx *types.Transaction) (*types.Transaction, error) {

tools/generators/ethlike/contract_template_content.go

@@ -64,6 +64,9 @@ func New{{.Class}}(
 	// FIXME bumps beyond 1.9.25.
 	key := accountKey.PrivateKey
 	keyAddress := crypto.PubkeyToAddress(key.PublicKey)
+	if chainId == nil {
+		return nil, fmt.Errorf("no chain id specified")
+	}
 	transactorOptions := &bind.TransactOpts{
 		From: keyAddress,
 		Signer: func(_ types.Signer, address common.Address, tx *types.Transaction) (*types.Transaction, error) {