Reproduction steps:

1. Open "1151547" project
2. Create a Ragdoll with the Model in the "SampleScene"
3. Enter Play mode to check that the Ragdoll works
4. Save the Scene
5. Create a New Scene
6. Load "SampleScene" scene
7. Enter Play mode
8. Notice that the Ragdoll no longer exists

Expected Result: Creating a Ragdoll dirties the scene
Actual Result: Creating a Ragdoll does not dirty the scene

Reproduced with: 2019.3.0a4, 2019.2.0b4, 2019.1.4f1, 2018.3.14f1, 2017.4.28f1
Did not reproduce on: 2018.4.1f1, 2018.4.0f1