The crash was caused by the selection attribute not being
initialized properly. The size was 0.
The fix uses `ed::curves::ensure_selection_attribute` to ensure
the attribute is created and on the right domain.
Extrude should only work for a point selection, so the poll
function of the operator is updated to reflect this.
Pull Request: https://projects.blender.org/blender/blender/pulls/130333
d3d26233fc