When Constructing bezier splines from dna, the positions of the
left/right handles were set directly in the internal vectors, by
requesting a reference to them. The problem is that
BezierSpline::handle_positions_left() calls ensure_auto_handles()
before returning the reference. That function does some calculations on
uninitialized memory if the positions array is not yet filled.
Differential Revision: https://developer.blender.org/D13107
7aa39b40f4