Scrap Mechanic v0.1.19d

Fixed an issue related to the multithreading update that randomly crashed the game. Fixed an issue that would sometimes make creations and players in them disappear. Disappeared creations and players should respawn at the starting position. Fixed an issue that could make creations with thrusters on them disappear if the game crashed while they were on a lift. Fixed a crash that could occur when exiting a game.