Caused by 1cca960677.
That commit stated that creating the final subdivided attribute didn't
free the "proc" attribute buffer that contains the data from the Curves
control points. However that wasn't the case, given the call to
`GPU_VERTBUF_DISCARD_SAFE` in that function. That caused a crash when
the overlay engine and EEVEE both wanted to access the VBO and it was
discarded the second time. To fix that, only regenerate the
`proc_attributes_buf` when it doesn't already exist.
This matches the "ensure" behavior that already exists for the
`cache.final[subdiv].attributes_buf` buffer, so conceptually it
seems fine.
Pull Request: https://projects.blender.org/blender/blender/pulls/119795
7f4a4fa605