Fix empty pathbar and broken monitoring after autofs timeouts

Currently, Nautilus stays in the same folder when autofs timeouts thanks to the b0e28bc1 merge request. However, there are some issues with this workflow:

• The most visible issue is that the pathbar is cleared and stays empty. I obviously forgot to cherry-pick also !1119 (d4ea8fcc) commit that deals with it.
• But also the monitoring and perhaps other stuff stop working for the current location because nautilus_window_slot_open_location_full does nothing in the case of the same location, but the underlying NautilusFile object is marked as gone...

This is an attempt to fix this, though I am not super sure this is the best way to deal with it...