On enabling 'UI Toolkit Live Reload' option in the 'Search asset store' window, NullReferenceException errors are thrown in console. Refer attached video and stack trace.

Steps to repro:
1. Create a new project
2. Window > Search > Asset Store
3. Right-click on Asset Store window > Enable 'UI Toolkit Live Reload' option

Actual Result:
Errors are thrown on enabling 'UI Toolkit Live Reload' in 'Search asset store' window

Expected Result:
On enabling 'UI Toolkit Live Reload' in 'Search asset store' window, it should work without throwing any errors in the console.

Occurring on:
2021.1.0a10, 2021.1.0a8

Working Fine:
2021.1.0a7

Note:
Quick Search is a Built-In Package in the Unity 2021.1.0a1
workaround: Disable the 'UI Toolkit Live Reload' option and reopen the 'Search asset store' window.

Environment:
Occurring on Windows 10 & macOS 10.15.