Removing session id from URL when closing details of session

[tajchert]

To reproduce:
Open schedule -> click any session for details -> detail screen of presentation appears, and URL changes to one with session id -> close presentation details card (ESC button or X) -> URL is still with session id
This result in that users in many cases copies URL with session id, when they don't want to do so, and are surprised why detail card appears.

Suggested solution:
Remove session id from URL when closing detail card.