How to reproduce:

1. Open the “SkinningEditorBreaks.zip“ project
2. Open “Assets\Leg_test.png“ in Sprite Editor
3. In Sprite Editor, switch to Skinning Editor
4. Enable the “Edit Geometry“ tool on the left
5. Delete the middle edge of the “Z” shape between the yellow and pink parts of the geometry
6. Observe the Sprite Editor and Scene view

Actual result: Both views break, 4 errors are displayed in the Console
Expected result: The views don’t break, and geometry is split into two parts correctly

Reproducible in: 2023.1.0a1, 6000.0.68f1, 6000.3.9f1, 6000.4.0b9, 6000.5.0a7

Reproduced on: Windows 11 Pro (25H2)
Not reproduced on: No other environment tested

Notes:
- The 4 errors displayed start with:
-- IndexOutOfRangeException: Index was outside the bounds of the array (U2D related)
-- GUI Error: You are pushing more GUIClips than you are popping. Make sure they are balanced
-- IndexOutOfRangeException: Index was outside the bounds of the array (UIElements related)
-- Matrix stack full depth reached
- If the changes are reverted, the views become usable again
- If the other seemingly unrelated geometries are deleted, the issue doesn’t reproduce, and the whole sprite becomes one big square geometry. This likely indicates that the free vertices (after deletion) try to connect to some distant vertex