Caused by rBf9567f6c63e7: Alembic: read/write generated coordinates of meshes.

So, if arbGeomParams were not defined, blender would crash.
This was reported for an alembic from (I think) Maya, blender itself
defines arbGeomParams at least as soon as normals are exported, but if
this is not the case, even .abcs from blender would crash.
Not totally sure were the orcos are supposed to be defined, but to fix the
crash, just make sure we actually have arbGeomParams.