fix(release_server): handle the case when requested values is empty (#4604)

Signed-off-by: Matthew Fisher <matt.fisher@microsoft.com>

pkg/tiller/release_server.go

@@ -139,7 +139,11 @@ func (s *ReleaseServer) reuseValues(req *services.UpdateReleaseRequest, current
 
 		// merge new values with current
 		if current.Config != nil && current.Config.Raw != "" && current.Config.Raw != "{}\n" {
+			if req.Values.Raw != "{}\n" {
 				req.Values.Raw = current.Config.Raw + "\n" + req.Values.Raw
+			} else {
+				req.Values.Raw = current.Config.Raw + "\n"
+			}
 		}
 		req.Chart.Values = &chart.Config{Raw: nv}
 

pkg/tiller/release_update_test.go

@@ -159,12 +159,11 @@ func TestUpdateRelease_ReuseValuesWithNoValues(t *testing.T) {
 				{Name: "templates/hello", Data: []byte("hello: world")},
 			},
 		},
-		Values:      &chart.Config{Raw: ""},
+		Values:      &chart.Config{Raw: "{}\n"},
 		ReuseValues: true,
 	}
 
-	_, err = rs.UpdateRelease(c, req)
-	if err != nil {
+	if _, err := rs.UpdateRelease(c, req); err != nil {
 		t.Fatalf("Failed updated: %s", err)
 	}
 }