Bezier Extraction matrices for 0th degree spline

[jzwar]

See #406 for more detail.

Bezier extraction matrix fails for following spline

test = sp.BSpline(
    degrees=[0, 0],
    control_points=[
        [0], [1], [2], [3],
    ],
    knot_vectors=[[0, .5, 1], [0, .5, 1]]
)

[mkofler96]

Is this the same reason why I cannot elevate the degree of a 0th degree BSpline?

The following code gives a segmentation fault:

test = sp.BSpline(
    degrees=[0],
    control_points=[
        [0],[1],[2]
    ],
    knot_vectors=[[0, .33, 0.66, 1]]
)

test.elevate_degrees([0])