How to reproduce:
1. Open the attached project
2. Open TestScene
3. Open Animation window (make sure that animation window's position is like in the video)
4. Select DragonBaby in the hierarchy
5. It has animation, detele some key frames
6. Undo operation (Ctrl+Z)
Result: Notice that in scene view tree reappears, but key frames don't appear in animation window, one needs to select window again

Reproducible: 5.5.0p3, 5.6.0b3
Not reproducible: 5.4.4f1