GUI error may occur when making and applying changes to SkinningEditor

Steps to reproduce:

1. Load the attached "6k6a6-pack copy" project
2. Open the "Fei" sprite in the Skinning Editor
3. Make changes to it (e.g. modify pivot) and save changes

Actual results: "EndLayoutGroup: BeginLayoutGroup must be called first." error gets thrown
Expected results: No errors are thrown

Reproducible with versions: 16.0.0

Notes:

• Basic functionality of 2D Animation doesn't seem to be affected

• It can occur repeatedly by constantly making and applying changes in the Skinning Editor

Full error message:
EndLayoutGroup: BeginLayoutGroup must be called first.
UnityEditor.GUIView:ProcessEvent (UnityEngine.EntityId,intptr,bool&) (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUIView.cs:70)

The following warnings also occur as the project is set to GPU skinning mode:

[Worker2] head is using a shader 'Universal Render Pipeline/2D/Sprite-Lit-Default' without GPU deformation support. Switching the renderer over to CPU deformation.
UnityEditor.AssetPreviewUpdater:CreatePreviewForAsset (UnityEngine.Object,UnityEngine.Object[],string) (at /Users/bokken/build/output/unity/unity/Editor/Mono/AssetPreviewUpdater.cs:12)