From b4f8d66bd32e2d8c8d9f35d23ded691261967ffd Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Wed, 4 Mar 2020 19:47:10 +0300
Subject: [PATCH] smartcontract: allow to marshal nil parameters

---
 pkg/smartcontract/param_context.go      | 6 +++++-
 pkg/smartcontract/param_context_test.go | 4 ++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/pkg/smartcontract/param_context.go b/pkg/smartcontract/param_context.go
index 147e00c9f..14f953f6b 100644
--- a/pkg/smartcontract/param_context.go
+++ b/pkg/smartcontract/param_context.go
@@ -66,7 +66,11 @@ func (p *Parameter) MarshalJSON() ([]byte, error) {
 	case BoolType, IntegerType, StringType, Hash256Type, Hash160Type:
 		resultRawValue, resultErr = json.Marshal(p.Value)
 	case PublicKeyType, ByteArrayType, SignatureType:
-		resultRawValue, resultErr = json.Marshal(hex.EncodeToString(p.Value.([]byte)))
+		if p.Value == nil {
+			resultRawValue = []byte("null")
+		} else {
+			resultRawValue, resultErr = json.Marshal(hex.EncodeToString(p.Value.([]byte)))
+		}
 	case ArrayType:
 		var value = make([]rawParameter, 0)
 		for _, parameter := range p.Value.([]Parameter) {
diff --git a/pkg/smartcontract/param_context_test.go b/pkg/smartcontract/param_context_test.go
index b6870e8eb..565ca95d6 100644
--- a/pkg/smartcontract/param_context_test.go
+++ b/pkg/smartcontract/param_context_test.go
@@ -30,6 +30,10 @@ var marshalJSONTestCases = []struct {
 		input:  Parameter{Type: ByteArrayType, Value: []byte{0x01, 0x02, 0x03}},
 		result: `{"type":"ByteArray","value":"010203"}`,
 	},
+	{
+		input:  Parameter{Type: ByteArrayType},
+		result: `{"type":"ByteArray","value":null}`,
+	},
 	{
 		input: Parameter{
 			Type:  PublicKeyType,