Calling UnityEditor.SceneView.GetAllSceneCameras() returns an empty array if it is called on start or the first update.

To reproduce:
1. Import repro package
2. Open repro scene
3. Enter play mode
4. Select the main camera - it has a monobehaviour component that calls GetAllSceneCameras() on Start(), the first Update() and later Updates.

Notice that only the later updates have a camera - the start and first update are empty.

In order to reproduce the issue the scene view must be visible at all times.