1. What version of Minecraft, Forge and Mod are you running?
   1. Minecraft v1.15.2
   2. Forge v31.2.36
   3. Prefab v1.5.0.9
   4. CTM v1.1.1.13
2. What type of issue is this? Choose one of the following:
   • Bug
   • Enhancement
3. Details:
   • After pressing the preview button in the Monster Structure, my game crashed. It looks like it crashed because of the CTM mod and the custom resource pack I had made with that mod.
     Crash Report
     Pack used: MC Connected CTM v1.0.zip

Please create an issue with the CTM team to address an issue that they have. There isn't anything I can do in my code outside of not letting you use the preview function when the CTM mod exists.

No, you're passing a nullable IModelData result to a non-null parameter. This is breaking the contract. Check for null and use EmptyModelData.