If the Asset Store filter in the Project Browser is selected before the results of a search are returned, assertion failures will occur. Note that the easiest way to reproduce this is to have the Asset Store filter selected before the search term is entered.

This is a regression in 2019.1.0a6.

1. Install Unity
2. Launch Unity
3. Create a new project with any settings
4. Once the project is created, go to the Project Browser
5. Enter any term into the search field to get the filters to appear
6. Select the Asset Store filter
7. Clear the search field
8. Enter a new search term

Expected Result:
The search should complete and show results without any errors.

Actual Result:
Two assertion failures appears in the console:

Unhandled group
Assertion failure. Value was False
Expected: True
UnityEditor.HostView:OnInspectorUpdate()

Unhandled group
Assertion failure. Value was False
Expected: True
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

Tested on Windows.

Ocurrs on:
2019.1.0a6, 2019.1.0a7, 2019.1.0a12

Does not Occur on:
2018.3.0f2, 2019.1.0a5