WICKET-5415 Wicket no more stores pages which were not rendered, even if they are stateful.
To do this we moved the code that marks the page as used from its constructor to #onInitialize() (IPageManager#touch(page)).
A ModalWindow with a Page needs to store the page to be able to reference it from the iframe.
With commit f36fa20 we added logic to fully initialize the modalwindow's page. This breaks use cases where the application needs to use any code that will lead to a redirect (e.g. setResponsePage(), or scheduleRequestHandler()).
The fix is to just touch the page, but not fully initialize it.