The slot had been there forever to address this same problem but only one of the two constructors actually set it, too bad that it was the wrong one...
This is something that normally won't be noticed. But if some actor is spawned on a moving platform, with both thinkers on the same statnum it means that the order of execution is not correct with the platform being done first, resulting in the actor to 'jump' while the platform is moving. To prevent this it is necessary that all sector movers only tick after all actors have completed their thinking turn.
We have to be extremely careful with the player data, because there's just too much code littered around that has certain expectations about what needs to be present and what not.
Obviously, when travelling in a hub, the player_t should be retained from the previous level. But we still have to set player_t::mo to the PlayerPawn from the savegame so that G_UnsnapshotLevel doesn't prematurely delete it and all associated voodoo dolls, because it checks player_t::mo to decide whether a player is valid or not.
The actual deletion of this redundant PlayerPawn should only be done in G_FinishTravel, after the actual player has been fully set up
* do not skip the player_t init when travelling in a hub. The old player may still be needed in some edge cases. This applies only to singleplayer for now. The multiplayer version still needs reviewing. I left it alone because it may shuffle players around which is not wanted when doing hub travelling.
* do not spawn two temp players in G_FinishTravel. Instead handle the case where no player_t::mo can be found gracefully by adding a few nullptr checks. This temp player served no real purpose except for having a valid pointer. The actual start position was retrieved from somewhere else.
- Fixed properties not having the proper indices.
- Use ViewPos-to-actor instead of measuring actor-to-actor.
- Use the actual camera instead of the actor so camera textures can work.
I wish I had realized this the last time it came up - it would have saved me a lot of trouble.
But as it turns out, the more recent travelling code makes all of this completely unnecessary, working perfectly fine with deleting the player pawns along with the rest of the thinkers before loading the stored ones from the savegame (and getting rid of those in G_FinishTravel.)
And with a sane savegame format that does not depend on side effects from how the thinker serializing handled linking into the lists the old code was even harmful, leaving voodoo dolls behind.
I had the exact same effect when I tried to reshuffle some things for reliably restoring portals, but did not make the connection to interference between two mutually incompatible player travelling mechanisms that just worked by sheer happenstance with the original order of things.
