Guards on chained methods on types

[kiltsonfire]

Rationale

Chained methods on our types can cause crashes if a method or a field in a struct is nil

Implementation

Should we put guards on these? Do we know these fields/method returns will always be non-nil?

Example:
// Type returns the transaction type.
func (tx *Transaction) Type() uint8 {
return tx.inner.txType()
}

// ChainId returns the chain ID of the transaction. The return value will always be
// non-nil.
func (tx *Transaction) ChainId() *big.Int {
return tx.inner.chainID()
}

[jdowning100]

As far as I know those fields should never be nil in a transaction.