So this happens on curves with only a single point in them.
If these are converted to the old particle system, we would end up with
a particle with only one key (invalid hair), then going to particle
editmode would crash.
The old particle system took care of this (e.g. when deleting keys in
`PARTICLE_OT_delete`)
See the following comment:
`/* We can't have elements with less than two keys. */`
So to resolve, only convert curves with multiple (>1) points in the
process.
Pull Request: https://projects.blender.org/blender/blender/pulls/118392
2f1b9432be