Blender Git Loki

Fix Freestyle (ASAN detected) crash

This was very simple to reproduce, just turn on Freestyle and press render.

Now to the truth of things. Most (if not all) of
~BlenderStrokeRenderer() can be removed. I believe this was done back
when freestyle was using G.main, and since we gave freestyle its own
main we can just leave the cleanup for later.

I will leave this for freestyle maintainers to think over though.

Note: There is a chance this was the issue reported on T57890. I will
wait for the reporter to confirm this as fixed though.