WebHost: Avoid KeyError in LttP multitracker when non-LttP games are present

[remyjette]

What is this fixing or adding?

If you navigate to the LttP mutlitracker in a multiworld with non-LttP games, the non-LttP game will cause a KeyError because player_location_to_area only contains the LttP games:

File "\WebHostLib\tracker.py", line 1686, in get_LttP_multiworld_tracker
    if location not in player_locations or location not in player_location_to_area[player]:
KeyError: 1

Reported in the replies of https://discord.com/channels/731205301247803413/1152293234677133324

How was this tested?

Loaded WebHost.py after this change, the page loads again.