The `smooth_curve_attribute` function smoothes individual
ranges of points that are selected within a stroke.
When smoothing a single range, the `gaussian_blur_1D` function
shouldn't treat this range as cyclic.
Instead, we check if the entire curve is selected and only use
the `cyclic` boolean in this case. For ranges, we always
treat them as non-cyclic.
Pull Request: https://projects.blender.org/blender/blender/pulls/132850
b4d5e256cb