Issue with demo_laplacian.py

I forgot the last lines, actually:

Level 2 Warning in ../../src/getfem/getfem_model_solvers.h, line 108: gmres did not converge!
Singular tangent matrix: perturbation failed, aborting.
solve done!
Von Mises range:  4.762201526816372e-48 5.522396422172957e-45
*** GetFEM view of the workspace:
message from gf_workspace follow:
Workspace 0 [main -- 13 objects]
 ID   0               gfMesh          
 ID   1            gfMeshFem           depends on  ID0
 ID   2            gfMeshFem           depends on  ID0
 ID   3            gfMeshFem           depends on  ID0
 ID   4              gfInteg          
 ID   5             gfMeshIm           depends on  ID0
 ID   6                gfFem          
 ID   7                gfFem          
 ID   8                gfFem          
 ID   9              gfModel           depends on  ID1 ID5
 ID  10            gfMeshFem           depends on  ID0
 ID  11                gfFem          
 ID  12              gfSlice           depends on  ID0


*** Python view of the workspace:
<class 'getfem.getfem.Mesh'> class 8, id 0 : instances=1
<class 'getfem.getfem.MeshFem'> class 9, id 1 : instances=1
<class 'getfem.getfem.MeshFem'> class 9, id 2 : instances=1
<class 'getfem.getfem.MeshFem'> class 9, id 3 : instances=1
<class 'getfem.getfem.MeshIm'> class 10, id 5 : instances=1
<class 'getfem.getfem.Model'> class 14, id 9 : instances=1
<class 'getfem.getfem.MeshFem'> class 9, id 10 : instances=1
<class 'getfem.getfem.Slice'> class 16, id 12 : instances=1
You can view the tripod with (for example) mayavi:
mayavi2 -d tripod.vtk -f WarpVector -m Surface
or
gmsh tripod.pos
Traceback (most recent call last):
  File "/Users/francescobonaldi/getfem-HEAD/interface/tests/python/demo_tripod.py", line 146, in <module>
    fig.show(mfu, deformation=U, data=(mfdu,VM), deformation_scale='20%')
  File "/Users/francescobonaldi/getfem-HEAD/interface/tests/python/getfem_tvtk.py", line 452, in show
    self.show_mesh_fem(mf, **args)
  File "/Users/francescobonaldi/getfem-HEAD/interface/tests/python/getfem_tvtk.py", line 410, in show_mesh_fem
    self.actors += it.vtk_actors()
                   ^^^^^^^^^^^^^^^
  File "/Users/francescobonaldi/getfem-HEAD/interface/tests/python/getfem_tvtk.py", line 299, in vtk_actors
    self.mapper = tvtk.PolyDataMapper(input=data);
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "tvtk_classes/poly_data_mapper.py", line 47, in __init__
  File "/opt/homebrew/lib/python3.11/site-packages/tvtk/tvtk_base.py", line 427, in __init__
    super(TVTKBase, self).__init__(**traits)
  File "/opt/homebrew/lib/python3.11/site-packages/traits/trait_type.py", line 90, in _read_only
    raise TraitError(
traits.trait_errors.TraitError: The 'input' trait of a PolyDataMapper instance is 'read only'.

I also tried to link OpenBLAS (installed with Homebrew) instead of MacOS default BLAS, but the outcome is the same. I can visualize tripod.pos in Gmsh, but of course, as you can see, the von Mises stress is null everywhere…

On the other hand, python demo_tripod_alt.py works well. Might it depend on the fact that I am using SuperLU and you are using MUMPS, perhaps?