Describe the Bug

Related to #1036, and I think this is now causing an issue with saving on trains for creative crates,

Since the item is null but the save code iterates over it anyways, and this causes a crash here:

So it should be fine to just add a check for stack being null and the crash will be avoided

Reproduction Steps

1.Build a train
2.Put a creative crate on the train
3.Open the pause menu to trigger a save or close the game

Expected Result

Not to crash

Screenshots and Videos

Note that this is from a development environment, but the issue still happens outside
latest.log
crash-2024-08-01_23.21.16-server.txt

Crash Report or Log

https://github.com/user-attachments/files/16462392/crash-2024-08-01_23.21.16-server.txt

Operating System

Windows 11

Mod Version

0.5.1f

Minecraft Version

1.20.1

Other Mods

No response

Additional Context

No response

Can't reproduce.
The stack should never ever be null, something else is wrong.
More debugging would be appreciated.

Ive gone back onto a backup of the world with the same everything and now i cant reproduce either :/
Ill look out for it in the future but it may have just been a fluke or some other issue at the same time.
My only thought is if its a missing mapping causing the item to become null after the tag has been read, but with testing this doesent work either, thanks for your time though,