Entering play mode while configuring avatar throws InvalidOperationException error and when exiting play mode, editor returns to the previous scene without saving any changes

To reproduce:
1. Open attached project "animationavatar.zip"
2. Open "k.unity" scene
3. Select Assets > Ethan > EthanAvatar and press Configure Avatar
4. Make any changes to the scene example (change Transform Position X from 0 to 1)
5. Enter play mode, observe in console InvalidOperationException
6. Exit play mode

Expected result: editor returns to Avatar Configuration scene
Actual result: editor returns to previous opened scene without saving any changes

Reproduced on: 5.5.0f3 5.6.1p2 2017.1.0b8 2017.2.0a1

Notes: even if you save the scene before pressing play, the new scene saves the name but the animations does not work, because EthanAvatar did not save the changes inside itself