Reproduction steps:
1. Open project attached (or create new one).
2. Create new object and timeline for it.
3. Create animation.
4. Add animation track to Timeline.
5. Drag Animation to animation track.

Expected result: Animation will be added to animation track.
Actual result: Animation is added to animation track, bet errors "NullReferenceException: Object reference not set to an instance of an object" appear in console.

Note: After pressing somewhere, this error stops.

Reproduced on: 2017.1.0b1