message: Properly remove persistentWidget from WidgetStore
  Fixes
diff: @@ -218,6 +218,7 @@ export default class AppTile extends React.Component {
  // Delete the widget from the persisted store for good measure.
  PersistedElement.destroyElement(this._persistKey);
  + ActiveWidgetStore.destroyPersistentWidget(this.props.app.id);
  if (this._sgWidget) this._sgWidget.stop({ forceDestroy: true });
  }
  