as: Support returning no normalized payload

pkg/messageprocessors/javascript/javascript.go

@@ -310,13 +310,14 @@ func (*host) decodeUplink(
 		return errOutput.WithCause(err)
 	}
 	msg.DecodedPayload, msg.DecodedPayloadWarnings = decodedPayload, output.Decoded.Warnings
+	msg.NormalizedPayload, msg.NormalizedPayloadWarnings = nil, nil
 
 	if normalized := output.Normalized; normalized != nil {
 		if errs := normalized.Errors; len(errs) > 0 {
 			return errOutputErrors.WithAttributes("errors", strings.Join(errs, ", "))
 		}
 		if normalized.Data == nil {
-			return errOutput.New()
+			return nil
 		}
 		// The returned data can be an array of measurements or a single measurement object.
 		var measurements []map[string]interface{}

pkg/messageprocessors/javascript/javascript_test.go

@@ -640,6 +640,49 @@ func TestDecodeUplink(t *testing.T) {
 		a.So(errors.IsAborted(err), should.BeTrue)
 	}
 
+	// Return no normalized payload (data is nil).
+	{
+		script := `
+			function decodeUplink(input) {
+				return {
+					data: {
+						state: input.bytes[0]
+					}
+				}
+			}
+
+			function normalizeUplink(input) {
+				return {
+					data: null
+				}
+			}
+			`
+		err := host.DecodeUplink(ctx, ids, nil, message, script)
+		a.So(err, should.BeNil)
+		a.So(message.NormalizedPayload, should.BeNil)
+		a.So(message.NormalizedPayloadWarnings, should.BeEmpty)
+	}
+
+	// Return no normalized payload (no return value).
+	{
+		script := `
+			function decodeUplink(input) {
+				return {
+					data: {
+						state: input.bytes[0]
+					}
+				}
+			}
+	
+			function normalizeUplink(input) {
+			}
+			`
+		err := host.DecodeUplink(ctx, ids, nil, message, script)
+		a.So(err, should.BeNil)
+		a.So(message.NormalizedPayload, should.BeNil)
+		a.So(message.NormalizedPayloadWarnings, should.BeEmpty)
+	}
+
 	// Decode and normalize a single measurement with out-of-range value.
 	{
 		message := &ttnpb.ApplicationUplink{