fix null pointer in jaeger-spark-dependencies

fixes jaegertracing/jaeger-operator#1113

Signed-off-by: Moritz Johner <[email protected]>

cmd/opentelemetry/app/exporter/elasticsearchexporter/esmodeltranslator/modeltranslator.go

@@ -134,7 +134,7 @@ func toTime(nano pdata.TimestampUnixNano) time.Time {
 func references(links pdata.SpanLinkSlice, parentSpanID pdata.SpanID, traceID dbmodel.TraceID) ([]dbmodel.Reference, error) {
 	parentSpanIDSet := len(parentSpanID.Bytes()) != 0
 	if !parentSpanIDSet && links.Len() == 0 {
-		return nil, nil
+		return []dbmodel.Reference{}, nil
 	}
 
 	refsCount := links.Len()

cmd/opentelemetry/app/exporter/elasticsearchexporter/esmodeltranslator/modeltranslator_test.go

@@ -159,6 +159,33 @@ func TestConvertSpan(t *testing.T) {
 	}, spans[0])
 }
 
+func TestSpanEmptyRef(t *testing.T) {
+	traces := traces("myservice")
+	span := addSpan(traces, "root", traceID, spanID)
+	span.SetStartTime(pdata.TimestampUnixNano(1000000))
+	span.SetEndTime(pdata.TimestampUnixNano(2000000))
+
+	c := &Translator{}
+	spans, err := c.ConvertSpans(traces)
+	require.NoError(t, err)
+	assert.Equal(t, 1, len(spans))
+	assert.Equal(t, &dbmodel.Span{
+		TraceID:         "30313233343536373839616263646566",
+		SpanID:          "3031323334353637",
+		StartTime:       1000,
+		Duration:        1000,
+		OperationName:   "root",
+		StartTimeMillis: 1,
+		Tags:            nil,
+		Logs:            nil,
+		References:      []dbmodel.Reference{}, // should not be nil
+		Process: dbmodel.Process{
+			ServiceName: "myservice",
+			Tags:        nil,
+		},
+	}, spans[0])
+}
+
 func TestEmpty(t *testing.T) {
 	c := &Translator{}
 	spans, err := c.ConvertSpans(pdata.NewTraces())