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Undo breaks lattice
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System Information
Operating system: Linux-5.2.0-arch2-1-ARCH-x86_64-with-arch 64 Bits
Graphics card: Mesa DRI Intel(R) HD Graphics 620 (Kaby Lake GT2) Intel Open Source Technology Center 4.5 (Core Profile) Mesa 19.1.2

Blender Version
Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-07-18 14:52, hash: rB38d4483c6a51
Worked: (optional)

Short description of error
Undoing a lattice edit results in somewhat arbitrarily mangled mesh.

Exact steps for others to reproduce the error

  1. Create an icosphere.
  2. Create a lattice.
  3. Scale lattice, so it's larger than sphere.
  4. Add lattice modifier to sphere and select the lattice.
  5. Select lattice, enter edit mode.
  6. Move lattice point.
  7. "Subdivide" lattice in the modified direction.
  8. Move a newly created lattice point.
  9. Undo "a couple of times." (usually once or twice)

Result - completely mangled mesh (sometimes scrunched up, sometimes stretched to infinity).

I have attached images explaining the process and the result.
First picture shows the state after state "4;" second image shows state "6;" third image shows "8;" and the last image is the result, in this case after three Undos.

Event Timeline

Actually, a much simpler steps are to:

  1. Create a lattice
  2. Move any point
  3. Increase lattice resolution in any direction
  4. Undo

I think it's pretty obvious that the issue is that undo does not undo the resolution change and ends up assigning garbage values to the previously inexistent vertices.