`visualise_orientations_pole_figure_mtex` broken when specifying only a single pole figure direction?

[aplowman]

Test workflow:

doc:
  - >
    Demonstration of a task to sample texture from a model orientation distribution
    function (ODF) using MTEX, and produce pole figures of the sampled orientations.

tasks:
  - schema: sample_texture_from_model_ODF_mtex
    inputs:
      crystal_symmetry: hexagonal
      specimen_symmetry: orthorhombic
      num_orientations: 1000
      ODF_components:
        - type: unimodal
          component_fraction: 0.4 # component fractions must sum to 1!
          modal_orientation_HKL: [0, 0, 1]
          modal_orientation_UVW: [1, 0, 0]
          halfwidth: 15
        - type: unimodal
          component_fraction: 0.3 # component fractions must sum to 1!
          modal_orientation_euler: [0, 0, 10] # in Bunge/degrees/MTEX hex alignment (y//b)
          halfwidth: 5
        - type: uniform
          component_fraction: 0.3 # component fractions must sum to 1!
      compile: false

  - schema: visualise_orientations_pole_figure_mtex
    inputs:
      crystal_symmetry: hexagonal
      use_contours: true
      compile: false
    sequences:
      - path: inputs.pole_figure_directions
        values:
          - - [0, 0, 0, 1]
            - [1, 0, -1, 0]
            - [1, 1, -2, 0]
          - - [0, 0, 0, 1]

[aplowman]

I don't see any problems with this. The first element plots three pole figures and second element plots a single pole figure.

Awaiting more info.