This was due to a missing endpoint case that wasn't handled in the port.
The last point still have to be discarded manually because of the
dot/stroke setting of the material.
The first test `ma1.x == -1` is not necessary anymore since the index
buffer do not contain this point (which was rendered using instance
rendering before.
Reviewed By: jbakker
Differential Revision: https://developer.blender.org/D16812
4cb2204d3a