igl sparsematrix return types are all empty now

[alecjacobson]

I'm not sure if it's a version mismatch. Others are reporting issues with pybind11 not matching scipy. It's tricky to update igl's pybind11 because of our dependency on numpyeigen which uses new_numpy_hacks_stable on https://github.com/fwilliams/pybind11.git which is 200+ commits behind pybind11 main.

posting here in case anyone else is suffering from the same issue and knows a solution.

[alecjacobson]

I think I've tracked the issue down to the numpy >=2.0.0 . Sparse Matrices still seem to work fine up to and including numpy<=1.26.4

I've heard from https://github.com/sgsellan/gpytoolbox/ that bumping pybind11 fixed this. Ideally @fwilliams could do this on his hacks branch.