338140f1e6
Introduced in d527e3a6bd.
The change to update PBVH normals before destroying the PBVH to fix
shading on duplicate meshes issues had the unfortunate side effect of
causing crashes for multires due to a race condition. This commit
simply avoids performing this flushing for multires to allow for
further iteration in the future instead of reverting the offending
commit entirely.
Pull Request: https://projects.blender.org/blender/blender/pulls/125268