Reproduction steps:
1. Open the attached "repro_IN-48526.zip" project
2. In the Project window, go to "Assets > Sprites" and select "5"
3. In the Inspector, press the "Open Sprite Editor" button
4. In the overlay of the Sprite Editor tab, press on the dropdown that says "Sprite Editor" and select "Skinning Editor"
5. Double-click on any part of the white flower or the butterfly
6. In the "Geometry" section on the left, select "Edit Geometry"
7. Double-click on one of the vertexes

Expected result: Mesh does not disappear
Actual result: Mesh disappears

Reproduced with: 7.0.11 (2021.3.29f1), 9.0.3 (2022.3.7f1), 10.0.2 (2023.1.9f1, 2023.2.0b5)

Reproducible on: Windows 10
Not reproducible on: No other environment tested

Note: Mesh can only be recovered by doing the same reproduction steps on another .psb file or restarting the Editor