Marshalling null instead of empty slice in Raw().

jwriter/writer.go

@@ -46,10 +46,17 @@ func (w *Writer) RawString(s string) {
 // RawByte appends raw binary data to the buffer or sets the error if it is given. Useful for
 // calling with results of MarshalJSON-like functions.
 func (w *Writer) Raw(data []byte, err error) {
-	if w.Error == nil && err != nil {
+	if w.Error != nil {
+		return
+	}
+
+	switch {
+	case err != nil:
 		w.Error = err
-	} else if w.Error == nil {
+	case len(data) > 0:
 		w.Buffer.AppendBytes(data)
+	default:
+		w.RawString("null")
 	}
 }