Crashes on startup when Electroblob's Wizardry 4.3.x is installed
https://pastebin.com/czDFkPkH
Electroblob77/Wizardry#542

https://github.com/TheidenHD/DoubleSlabs/releases/tag/0.11.1

Same !

Ok everything i figured out so far:
cjminecraft.doubleslabs.client.ClientConstants.getFallbackModel
is only called on startup when Wizardry is installed.

Minecraft.getMinecraft().getBlockRendererDispatcher()
returns null wen it is called on startup.

Minecraft.blockRenderDispatcher
is only initialized after the Minecraft.run method is called

Thanks for reporting this, it appears that this has now been fixed :)