I've run into two cases where Iris has an internal error while loading shaders that I'm working on. I've already posted one to the github issues (link: https://github.com/IrisShaders/Iris/issues/2598), but that has had no activity and I now have another error for another project. The only "error report" it gives is "Unknown error loading Distant Horizons compatibility.", and I've attached the log file. I'm using Minecraft 1.20.1, Iris 1.8.1+1.21.1-fabric, and Distant Horizons 2.2.1-a-1.21.1