undefined labels don't list key= before the __undefined__ value

pkg/kubecost/asset.go

@@ -109,9 +109,10 @@ func key(a Asset, aggregateBy []string) (string, error) {
 			if labelKey := strings.TrimPrefix(s, "label:"); labelKey != "" {
 				labelVal, ok := a.Labels()[labelKey]
 				if !ok {
-					labelVal = "__undefined__"
+					key = "__undefined__"
+				} else {
+					key = fmt.Sprintf("%s=%s", labelKey, labelVal)
 				}
-				key = fmt.Sprintf("%s=%s", labelKey, labelVal)
 			} else {
 				// Don't allow aggregating on label ""
 				return "", fmt.Errorf("Attempted to aggregate on invalid key: %s", s)

pkg/kubecost/asset_test.go

@@ -697,8 +697,8 @@ func TestAssetSet_AggregateBy(t *testing.T) {
 	}
 	fmt.Println(as.assets)
 	assertAssetSet(t, as, "1e", window, map[string]float64{
-		"test=__undefined__": 53.00,
-		"test=test":          7.00,
+		"__undefined__": 53.00,
+		"test=test":     7.00,
 	}, nil)
 
 	// 2  Multi-aggregation