[Bug]: Neoforge 1.21.1 Crash on clicking "singleplayer." in main menu.

[NerdySpider]

Bug Description

Hello there! A friend of mine is trying to set up a pack for me and some friends to play, they normally don't use things like github so they wanted me to post this on their behalf!

I'm not 100% sure myself what an exact issue is, however it does point to something about some parts being missing, I'm more of a 1.12.2 player myself so I'm not too used to modern, sorry if this ends up being something obvious! There is Sable in this pack too for Aeronautics, so this could be an issue caused by it, however my friend did say this issue still happened without Sable.

How to Reproduce?

1. Use the modlist (found at the bottom of the report)
2. Load up the pack.
3. Crash on clicking singleplayer.

Expected Behavior

World preparation should begin.

Version

1.16.22

Mod Loader Version

1.21.1

Mod Loader

NeoForge

Logs or additional context

https://mclo.gs/uHKeQpi
Modlist is also at the bottom of the log if needed.

Code of Conduct

• I have searched the issue tracker and confirmed that the issue has not been reported
• I have checked the FAQ (if one is present) and my issue is not listed
• I have verified that I am using the latest version of the mod
• I have verified that I have installed all the required dependencies for the mod
• I have verified that I do not have Optifine installed. We will close issues if we detect Optifine is in your pack. We cannot fix Optifine issues. Please do not report issues with Optifine present.

[Mrbysco]

Both Stellaris and Ad Astra use a data/<modid>/planets/ folder for their planet JSONs.

Stellaris is trying to read Ad Astra's planets and crashes because it's expecting their format to be used.

This is not an issue with Ad Astra

[NerdySpider]

Ah okay, thank you for letting me know!