Fix crashes caused by null PlayerExtraOptionsPanel

[SadPencil]

In GameLobbyBase.cs:

protected PlayerExtraOptions GetPlayerExtraOptions() =>
    PlayerExtraOptionsPanel == null ? new PlayerExtraOptions() : PlayerExtraOptionsPanel.GetPlayerExtraOptions();

And in PlayerExtraOptions.cs:

public List<TeamStartMapping> TeamStartMappings { get; set; }  // this is by default null

Which causes a crash of a null pointer at PlayerExtraOptions.ToString(), where:

TeamStartMapping.ToListString(TeamStartMappings) // TeamStartMappings is null, while ToListString() crash on null

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Also, in MultiplayerGameLobby.cs:

PlayerExtraOptionsPanel.SetIsHost(isHost);

PlayerExtraOptionsPanel can be null.

[github-actions[bot]]

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[SadPencil]

I had to apply these same changes to my build in order to be able to run TS. Does this mean TS is currently broken? Is this specific to TS?

I encounter this problem when testing on migrating MO 336 which is an Ares build. So I think it is broken in all builds.