The bug

The block marker particle displays the missing texture if air, cave_air or void_air are the particles requested.

How to reproduce

1. /particle minecraft:block_marker air
2. Note the missing texture that results

Expected results

As air is invisible, this command would produce a completely invisible particle.

Actual results

The missing texture, a texture intended to only appear when resource packs are misconfigured, is seen instead.

How to fix

Currently, the particle field is pretty much required for model files. If absent, the missing texture is used (this goes unreported in the game logs and as such cases of it happening tend to go unnoticed - see MC-236295). It may be worth introducing some option to model files (for example, a top level "no_particles" = true) which makes all particles requested of the model either invisible or does not generate any particles at all.