Steps to reproduce:

1. Open attached project:
2. Open scene "Scene"
3. Select "GameObject" in hierarchy and open animation window to view its animation
4. Notice that there is Animation Event at 0:05 mark
5. Right click on it and open Edit window
6. Notice "Function Not Supported"
7. Run scene and notice NullReferenceException: Object reference not set to an instance of an object thrown in console

Regression introduced in: 5.3.0f1 (b948b362cb65)

Expected behaviour: Prior to regression the following message was printed in console: "Failed to call AnimationEvent MyFunction of class EventReceiver. The function must have either 0 or 1 parameters and the parameter can only be: string, float, int, enum, Object and AnimationEvent."