Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 980 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 452.06
Broken: version: 2.91.0 Alpha, branch: master, commit date: 2020-08-31 03:47, hash: rB68797982025c
Worked: 2.82 (sub 7), branch: master, commit date: 2020-02-12 16:20, hash: rB77d23b0bd76f
Short description of error
Blender crashes when you CTRL-Z back to sculpt mode when the mesh has shape-keys. This bug happens in 2.83.0 and up, only in the Windows builds. Tested in Linux Mint 19.3 and had no crash there.
Exact steps for others to reproduce the error
Add basis shape-key on any mesh -> change to sculpt mode -> Change mode to edit -> Undo back -> This causes a crash when it undoes back to sculpt mode.