Toggle stack should trigger a render, not a refresh

public/app/plugins/panel/graph/tab_display.html

@@ -114,7 +114,7 @@
       label="Stack"
       label-class="width-7"
       checked="ctrl.panel.stack"
-      on-change="ctrl.refresh()"
+      on-change="ctrl.render()"
     >
     </gf-form-switch>
     <gf-form-switch