Version: 2.0.0+1.19
Minecraft Version: 1.19
Using the Fabulously Optimized modpack version 4.0.0-alpha.1
Crash log: https://paste.ee/p/Z5vqv
Relevant section:

java.lang.NullPointerException: Cannot invoke "net.fabricmc.fabric.api.renderer.v1.Renderer.meshBuilder()" because the return value of "net.fabricmc.fabric.api.renderer.v1.RendererAccess.getRenderer()" is null
	at me.pepperbell.continuity.impl.client.ProcessingContextImpl.<init>(ProcessingContextImpl.java:19)
	at me.pepperbell.continuity.client.model.CTMBakedModel$CTMQuadTransform.<init>(CTMBakedModel.java:70)
	at me.pepperbell.continuity.client.model.ModelObjectsContainer.<init>(ModelObjectsContainer.java:10)

Not entirely sure how to reproduce as I was just walking around in a newly created world, but the crash indicates it involves falling gravel blocks. Likely just a simple null check needed.

Install Indium. The CurseForge and Modrinth pages explicitly say this in bold letters.

If Indium is required to not crash, then shouldn't it be specified in the fabric.mod.json?

No, because it is only required if Sodium is installed.

I have been informed that Indium doesn't work in 1.19 yet. So...

There is an unofficial port that you can use or you can wait or uninstall Sodium.