How to reproduce:
1. Open the attached Unity project
2. Open SampleScene scene
3. Select player-test game object
4. Drag a couple of sprites to the selected game object to create an animation
5. Take couple more spreites and repeat step 4. Use the same name to create an animation
6. Dialog opens. Replace current animation with a new one
7. Observe the Animation window

Expected result: Animation is replaced with a new one
Actual result: Animation window stops showing Animation name. In the Animator window, there is an empty state as well.

Reproduced with: 2021.2.0a18, 2021.2.0a19, 2021.1.0b7, 2022.1.0a1, 2022.1.0a5.
Couldn't reproduce with: 2021.2.0a1, 2021.2.0a17

Notes:
You can select the player-idle-1 game object and check the Animation and Animator windows. The bug is visible there without doing repro steps.