The evaluated mesh is now only recomputed when the required data layers
are missing. Previously the evaluated mesh was re-evaluated incorrectly,
which caused the stippled result and the failing assert.
Since now only the evaluated mesh is used, and never a temporary mesh,
there is also no more need to keep track of whether the mesh needs
freeing or not.
Reviewed By: sergey
Differential Revision: https://developer.blender.org/D8574
5195d346f4