Blender Git Loki

Add versioning code to make particles with default size visible again

Due to changes in draw code particles from old files that may have had a
default draw size of 0 will not be visible. Old draw code would check
for this and adjust the size, however the unit for draw size has changed
from pixels to BU, and it no longer makes sense to have such checks.

This patch is to ensure particles from such files remain visible.