ArgumentException is thrown on a console while selecting folders inside "Packages" folder from Two Column Layout project tab.

Steps to reproduce:
1. Create a new project.
2. Select "Two Column Layout" from a dropdown of project tab
3. Window > Package Manager > Remove any package.
4. Select Packages folder from Project tab.
5. Select any subfolder of package folder from second column of project view.

Actual Result.
1. ArgumentException is thrown in console.
2. Icons of subfolder disappear in the second column of project tab.

Expected result.
Project tab should show content inside subfolders.

Reproducible on
2018.2.0b3, 2018.2.0b2.

Note:
1. On 2018.2.0b1 to 2018.2.0a5, user is unable to select Package folder from project tab.
2. On 2018.2.0a4 and lower versions, packages folder in project tab is not included.
3. Not sure if the packages folder should be showing inside the project window

Environment
Mac 10.13 , 10.12 and Windows 10

Stack Trace:
ArgumentException: Asset path cannot be empty.
Parameter name: assetPath
UnityEditor.PackageManager.Packages.GetForAssetPath (System.String assetPath) (at /Users/builduser/buildslave/unity/build/Modules/PackageManager/Editor/Managed/PackageManager.cs:25)
UnityEditor.ProjectBrowser.RefreshSearchText () (at /Users/builduser/buildslave/unity/build/Editor/Mono/ProjectBrowser.cs:580)
UnityEditor.ProjectBrowser.FolderTreeSelectionChanged (Boolean folderWasSelected) (at /Users/builduser/buildslave/unity/build/Editor/Mono/ProjectBrowser.cs:2381)
UnityEditor.ProjectBrowser.ShowFolderContents (Int32 folderInstanceID, Boolean revealAndFrameInFolderTree) (at /Users/builduser/buildslave/unity/build/Editor/Mono/ProjectBrowser.cs:924)
UnityEditor.ProjectBrowser+BreadCrumbListMenu.SelectSubFolder () (at /Users/builduser/buildslave/unity/build/Editor/Mono/ProjectBrowser.cs:2917)
UnityEditor.GenericMenu.CatchMenu (System.Object userData, System.String[] options, Int32 selected) (at /Users/builduser/buildslave/unity/build/Editor/Mono/GUI/GenericMenu.cs:121)