Crash during startup with Blockus on 0.115.6+2.1.3+1.21.1

[unilock]

Minecraft version

1.21.1

Describe the bug

On the latest version of FFAPI (0.115.6+2.1.3+1.21.1), the game will crash during startup if Blockus is installed with a NullPointerException (from FlammableBlockRegistryImpl#add).

Steps to reproduce

1. Install Sinytra Connector, FFAPI, and Blockus
2. Start the game
3. Crash

Logs

https://gist.github.com/unilock/c229809c2e55204b101513d382a7512e

Additional context

Downgrading FFAPI to v0.115.6+2.1.2+1.21.1 works around the issue.