“MissingReferenceException”, “NullReferenceException” and GUI errors are spammed in the Console when selecting “Boris” GameObject in the Prefab field of the “Plunkah” GameObject in the “_IK” Sample scene

Steps to reproduce:
1. Create new Unity project using Universal 2D Template
2. Import 2D Animation “Samples” via Package Manager
3. Open “_IK” Scene (Assets/Samples/2D Animation/14.0.3/Samples/Extras._IK.unity)
4. Select “Plunkah” GameObject in Hierarchy window
5. In Inspector window > click on “Prefab” field
6. Select “Boris” Game Object
7. Observe Console window

Actual results:  Errors are spammed in the Console window “MissingReferenceException”, “NullReferenceException”, “GUI Error: You are pushing more GUIClips than you are popping. Make sure they are balanced.”
Expected results: No errors are spammed in the Console window

Reproducible with versions: 6000.3.0b7 (1bec74c0745e), 6000.3.14f1, 6000.4.6f1, 6000.5.0b7, 6000.6.0a4
Not reproducible with versions: 6000.0.74f1, 6000.3.0b6 (211490bb75a6)

Tested on (OS): macOS Silicon Tahoe 26.4.1