If the project window view was set to One Column Layout before creating a new project, using search box shows package manager files in addition to projects assets.

To reproduce:
1. Create a new project
2. Set Project Window layout to One Column Layout
3. Close Unity and create a new project again
4. Make sure that the Project Window is still One Column Layout after creating a new project
5. Type in anything in the search box

Expected result: assets that are in the project are shown
Actual result: package manager files that match the search criteria are shown

Reproduced on: 2018.2.0a8
Did not reproduce on: 2018.1.0b13 2018.2.0a5

Notes:
This is a bad design as it might confuse users if their Project Window is set to one column and they create a new project. It should show Assets folder together with Package Manager OR using search in One Column Layout, it should only search in the Assets folder.