when a ViewNavigator has been added at runtime, the updated number of ViewNavigators isn't remembered by persistence manager

Steps to reproduce:
1. Run the app that has a SplitViewNavigator and two child ViewNavigators with the persistence manager enabled.
2. Add the third ViewNavigator to the SplitViewNavigator.
3. Close the app.
4. Re-launch the app.

With the bug project:

1. Launch the app.
2. Click "Add VN" button.
3. Close the app.
4. Re-launch the app.

Actual Results: Only two ViewNavigators showing.

Expected Results: Three ViewNavigators showing as lastly seen.

Workaround (if any):