How to reproduce:
1. Create a new project with older than 2019.2.0a5 Unity version
2. Export a default Scene and delete it from the project
3. Set the Project Tab view to one column layout
4. Update project to 2019.2.0a5 or later version
5. Try to drag the exported package into the project somewhere below the package folder in the Project tab

Expected result: The import process is started
Actual result: The package is not importing

Reproducible: 2019.2.0a5
Not reproducible: 2017.4.20f2, 2018.3.6f1, 2019.1.0b3, 2019.2.0a4

Notes:
- 2019.2.0a5 version doesn't have one or two column layout selection in the Project tab
- Workaround: Go to Window -> Layouts -> Revert Factory Settings...