Steps to reproduce:
1. Open user attached project
2. Select Bugs -> Switch Active Scene
3. Observe that no events are received,
4. Select Bugs -> Switch Unload Scene
5. Observe that only "scene-closing, scene closed" events are received
6. Select Bugs -> Load Scene Single
7. Observe that only "sceneOpening, sceneOpened" events are received

Expected results:
"activeSceneChanged" should be received when switching between active scenes
"activeSceneChanged" should be received when unloading the currently active scene
(in no particular order): activeSceneChanged, sceneClosing, sceneClosed should be received when loading a new scene in Single mode

Reproduced in: 2018.3.0a1, 2018.2.0b4, 2018.1.0f2, 2017.4.3f1, 2017.3.2f1, 2017.2.3f1, 2017.1.3p2