Support null serialization in SignedTransaction
@@ -156,7 +156,7 @@ public class SignedTransaction {
serializeArrayItems(builder, item.asArray());
builder.append("]");
} else {
- if (item == null) {
+ if (item == null || item.isNull()) {
builder.append("\\0");
} else {
builder.append(escape(item.asString()));
