Blocks falling back to the missing model show "random" section of the block atlas instead of the missing texture

When a block’s model fails to load for whatever reason and falls back to the “missing model”, placing said block in the world will show a “random” section of the block atlas instead of the missing texture. The attached resource pack triggers this on stone blocks.

This is caused by the way the model baking process resolves Material.Bakeds from the Materials specified in the model JSON. When any model is baked, both atlases are searched for the textures. This search checks the item atlas first and the block atlas second and only if the item atlas query returns null, causing textures existing on both atlases to be resolved to the item atlas. Since minecraft:missingno exists on all atlases, this behavior applies to it. Normally the block model baking has a subsequent check in SimpleModelWrapper.bake() to reject block models using item atlas sprites and fall back to the missing model. However, no such check exists in the special-cased baking of the “global” missing models in ModelBakery.MissingModels.bake() nor does said code attempt to force the use of the missing sprite from the block atlas. Since block models are unconditionally rendered with the block atlas, this causes the placed block to render whatever happens to be on the block atlas in the UV coordinate range occupied by the missing sprite on the item atlas.

The provided reproduction case runs into this issue twice: the non-existent model is replaced with the unbaked “missing model” during dependency resolution, this model is then baked with the incorrect sprite, gets caught by the aforementioned sanity check and then still breaks because the “global” missing models it tries to fall back to is broken.