MobSpawnESP is unstable and sometimes crashes the game with a NullPointerException.
Running on 1.16.4, Fabric API 0.25.4, Wurst v7.7.2-MC1.16.4, and Fabric Loader 0.10.6+build.214.
Enable MobSpawnESP, walk around, and eventually your game will crash.
P.S. Thanks to whoever programmed the MobSpawnESP hack. Wurst's implementation is insanely optimized and runs far better than any alternatives, for example that one mob spawn indicator mod from CurseForge.