Duplicated POI views when opening a POI from notifications and app was in background in a different POI

[isabelrios]

Steps
Open a notification with POI1
Leave that POI1 in background
Receive a different notification about POI2
Open POI2 view
Close POI2 view

Actual
It is necessary to close POI2 view twice. It is like the POI1 which was in background has changed to POI2 and so there are two POI2 views.

Please see video to understand it better:
https://youtu.be/-C1j6awqg-s

[wilsonpage]

@gmarty FYI I think this patch proves that two ItemScene can be mounted at the same time.

[wilsonpage]

#375