Add helper methods for nil checks in structs

priv_key.go

@@ -53,6 +53,10 @@ func (p *PrivKeyS) UnmarshalJSON(data []byte) (err error) {
 	return
 }
 
+func (p PrivKeyS) Empty() bool {
+	return p.PrivKey == nil
+}
+
 func PrivKeyFromBytes(privKeyBytes []byte) (privKey PrivKey, err error) {
 	err = wire.ReadBinaryBytes(privKeyBytes, &privKey)
 	return

pub_key.go

@@ -55,6 +55,10 @@ func (p *PubKeyS) UnmarshalJSON(data []byte) (err error) {
 	return
 }
 
+func (p PubKeyS) Empty() bool {
+	return p.PubKey == nil
+}
+
 func PubKeyFromBytes(pubKeyBytes []byte) (pubKey PubKey, err error) {
 	err = wire.ReadBinaryBytes(pubKeyBytes, &pubKey)
 	return

signature.go

@@ -51,6 +51,10 @@ func (p *SignatureS) UnmarshalJSON(data []byte) (err error) {
 	return
 }
 
+func (p SignatureS) Empty() bool {
+	return p.Signature == nil
+}
+
 func SignatureFromBytes(sigBytes []byte) (sig Signature, err error) {
 	err = wire.ReadBinaryBytes(sigBytes, &sig)
 	return