How to reproduce:

1. Open a new project
2. Select any gameobject
3. Open the Animation Window
4. Create a new Animation
5. Right-click before the 0:00 point in the timeline and select Add Animation Event
- Note that an animation event is created where it should not be created
- Reproduced in Version 5.4.0b1 (3137382c8e08), Version 5.2.4f1 (98095704e6fe), Version 5.3.1f1 (3b3e8231502f)
- This has no effect on actual animations as the event is never called when the animation is played