On enabling 'UI Toolkit Live Reload' option in the maximized 'Search' window, NullReferenceException is thrown in console. Refer attached video and stack trace.

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

Actual Result:
NullReferenceException is thrown on enabling 'UI Toolkit Live Reload' in maximized 'Search' window.

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

Occurring on:
2021.2.0a4, 2021.1.0b6, 2021.1.0a8

Working Fine:
2021.2.0a3, 2021.1.0a7

Note:
Quick Search is a Built-In Package in the Unity 2021.1.0a1

Environment:
Occurring on Windows 10 & macOS 10.15.