Blender Git Loki

Fix T88262: Curve to mesh crash with vector last segment

The code incorrectly used the size of the second to last segment rather
than the last segment's size. That was a problem when the last segment
is a vector segment but the second to last isn't.

I also used the opportunity to slightly refactor the control point
offsets cache, making it one longer so it also contains information
about the size of the last segment, simplifying other code.