Dependencies are not included while exporting a package with scene asset.

Steps to Reproduce:
1. Create a new project.
2. Add a GameObject to the scene.
3. Create a prefab of that game object.
4. Create a script and attach it to the game object in the hierarchy.
5. Save the scene.
6. Select the scene in the project window and right click to select export package.
7. Make sure you have selected include dependencies.

Actual Result: No dependencies are included while exporting scene.

Expected Result: Dependencies should be included. ( Prefab, Script should be included in this case)

Reproducible on: 2018.3.0a1, 2018.3.0a5

Working On: 2018.2.f2

Note:
- Appear Always
- Appears on both OSX and Windows