Using a resource pack with a block model with itself as a parent removes all textures

Expected behaviour (happens in 1.12.2)

The resource pack refuses to load, and textures return to the default.

Actual behaviour

All textures become the black and magenta "missing texture"

Steps to reproduce

1. Download the attached resource pack and put it in the resourcepacks folder
2. Enable the resource pack
3. Everything should become black and magenta