Fix eventsListener and infoListener stacking

[DudeKiller82]

When the app is started when a game launches:

• the background window calls setListeners
• the in game window or second screen calls setListeners In the function the removeListener call is supposed to remove the events from background an replace them by the one from ingame. This does not work because the object sent to the function are not the same. This results as events being triggered twice everytime. For example the moving event in rainboww six pops twice on each move. The fix here store the object of the last added event to be able to remove it afterward.

[OdedItkinOW]

Seems legit. This is a known issue in this sample app, that was fixed in future ones (like the events-sample-app), which will hopefully fully replace this current one in the near future. That being said, a fix is a fix, so I see no reason not to merge this, as it does seem to work.

Thanks for the pr!