Steps to reproduce:

1. Open attached project. (or create new one with two scenes, can be empty, no diff)
2. Open both scenes in additive.
3. Make some changes to second one.
4. Save the second scene onto the first one (replace).

Expected result: First scene should be marked as dirty. (or HandleOpenScenesChangeOnDisk should be called with reload scene dialog)
Actual result: Both scenes point to same asset, they look different in hierarchy and both are not dirty.

Note: Scene manager contains two instances of same scene asset, which is invalid according to SceneSet::IsValid and SceneManagerSetup::IsValid, opening same scene twice is also not possible.

Reproduced on: 5.5.0b3, 5.4.0f1