System Information
Operating system: Linux-5.2.14-1-default-x86_64-with-glibc2.17 64 Bits
Graphics card: GeForce GTX 1660 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 435.21

Blender Version
Broken: version: 2.91.0 Alpha, branch: master, commit date: 2020-08-28 21:41, hash: rB141a3e6d47ab
Worked: blender-2.90.0-9f5cc128d955-linux64 hash: rB9f5cc128d955
Broken since at least: blender-2.90.0-62aa103d485f-linux64 rB62aa103d485f

Short description of error

Crash when moving a vertex after duplicating and hiding a mesh with X axis mirror enabled

Exact steps for others to reproduce the error

• Open a new Blender default scene
• Tab into edit mode
• Switch to vertex select
• Select all vertices (a)
• Click X in the mirror settings at the top right (Mesh.use_mirror_x)
• Duplicate the vertices (shift+d)
• Cancel movement (right mouse button)
• Hide the duplicate mesh (h)
• Select the bottom-left-back vertex in the cube
• Grab vertex (g)
• Move mouse
• * CRASH *

Steps shown in the attached video file: