fix(chartutil): fix nil error on values

Fixes: https://github.com/kubernetes/helm/issues/803

pkg/chartutil/values.go

@@ -65,10 +65,12 @@ func tableLookup(v Values, simple string) (Values, error) {
 }
 
 // ReadValues will parse YAML byte data into a Values.
-func ReadValues(data []byte) (Values, error) {
-	out := map[string]interface{}{}
-	err := yaml.Unmarshal(data, &out)
-	return out, err
+func ReadValues(data []byte) (vals Values, err error) {
+	vals = make(map[string]interface{})
+	if len(data) > 0 {
+		err = yaml.Unmarshal(data, &vals)
+	}
+	return
 }
 
 // ReadValuesFile will parse a YAML file into a Values.

pkg/engine/engine_test.go

@@ -53,6 +53,10 @@ func TestRender(t *testing.T) {
 	if out["test1"] != expect {
 		t.Errorf("Expected %q, got %q", expect, out["test1"])
 	}
+
+	if _, err := e.Render(c, &chart.Config{}, overrides); err != nil {
+		t.Errorf("Unexpected error: %s", err)
+	}
 }
 
 func TestRenderInternals(t *testing.T) {