[1.20.1] [Forge] Not having Forgified Fabric API will cause the game to crash on world creation/join

[FlameyFaucet]

Bug Description

Modloader: Forge
Client: Curseforge
Description: The game will crash upon attempting to load or create a world when Forgified Fabric API isn't installed. If it is installed (even without Sinytra Connector, the mod the API is intended for), then everything will work fine. The mod references something only Fabric's API can supply under normal circumstances, so either this is an unmarked dependency (if intentional) or leftovers that shouldn't be acting this way. It seems to have been introduced on versions past 0.3.19 and hasn't really been caught because Sinytra Connector is present in a lot of modpacks.

Note: I have the Java flags -Dmixin.debug=true -Dmixin.checks.interfaces=true -Dmixin.verbose=true -Dmixin.debug.verbose=true -Dmixin.dumpTargetOnFailure=true enabled thus the log will include information that these flags expose. If it would be better without, please let me know.

Reproduction Steps

Simply add Embeddium and nothing else to your mod instance, open the game and try to generate a world or join an existing one. It will get past the chunk colormap but then abruptly terminate the internal server and crash to the launcher. Adding Forgified Fabric API will prevent this from happening.

Log File

latest.log

[FlameyFaucet]

I am a fool. An imbecile of my own making.
The Java flags I have enabled (-Dmixin.debug=true -Dmixin.checks.interfaces=true -Dmixin.verbose=true -Dmixin.debug.verbose=true -Dmixin.dumpTargetOnFailure=true) are the sole cause of this. Having them enabled (or, at least, one of them- God knows which, I'm not good enough at Java to know) when you launch the game will cause this crash to occur. Without them, even without FFAPI, nothing bad will happen and the game can function properly. Given that this is my own fault for not realizing Java flags could even do that, I'm closing this.