Scene Camer can be accessed through script by using GameObject.Find("SceneCamera").SetActive(false);

To reproduce:
1. Open attached project "Scene Camera Null.zip"
2. Enter play mode
3. Exit play mode
4. Try changing views or rotating camera in Scene View

Expected result: Scene view is normal as always
Actual result: Scene view looks like it is not attached to the camera anymore

Reproduced on: 2018.2.0a1

Can not test on older version since this script crashes Unity. Setting Is Regression - no.