GraphicsCompositor is broken in some cases

Release Type: Official Release

Version: 3.0.0.6

Platform(s): Windows

Describe the bug
See steps to reproduce and screenshots.

To Reproduce
[Case 1]

1. Create a NewGame project.

2. Open the GraphicsCompositor asset.

3. Edit Camera Renderer's Child(SceneRendererCollection).

   1. Change "Shared: Forward renderer" to "Clear".
   2. Change "Shared: Debug renderer" to "Shared: Forward renderer"(top forward renderer in dropdownlist).
   3. Add "Shared: Debug renderer".

4. Save and reload the project.

Result: "Editor renderer" is not connected to "Forward renderer".

[Case 2]

1. Create a NewGame project.

2. Open the GraphicsCompositor asset.

3. Edit Camera Renderer's Child(SceneRendererCollection).

   1. Change "SceneRendererCollection" to "None"
   2. Change "None" to "SceneRendererCollection"
   3. Add "Shared: Forward renderer"(top forward renderer in dropdownlist).
   4. Add "Shared: Debug renderer".

4. Save and reload the project.

Result: Some renderers are automatically added in SceneRendererCollection.

Expected behavior
GraphicsCompositor is saved and loaded without extra changes.

Screenshots
Case 1, step 3

Case 1, result

Case 2, step 3

Case 2, result

Log and callstacks

Additional context
Windows10 Pro x64(1803)
Visual Studio Community 2017(15.8.8)

Reproduce both cases in a NewGame project by editing the GraphicsCompositor asset and its Camera Renderer Child(SceneRendererCollection), then saving and reloading. Inspect the GraphicsCompositor and SceneRendererCollection handling involved in persistence; done means renderer connections remain unchanged and no extra renderers are added after reload.