\[Visual Scripting] Unable to expand Graph Inspector and Blackboard if the scrolling header is behind the expand cursor

Unable to expand Graph Inspector and Blackboard if the scrolling header is behind the expand cursor

Steps to repro:
1. Create a new Project
2. Project window > Create > Visual Scripting > Script Graph
3. Select Script Graph
4. Inspector > Edit Graph
5. Dock Script Graph window next to the scene window in 2 by 3 layout
6. Focus on Graph Inspector and Scroll to the very top
7. Drag to expand the Graph Inspector from next to the scrolling header

Actual Result:
The Graph Inspector doesn't expand

Expected Result:
The Graph Inspector should expand

Reproducible on: 2021.1.0b2, 2021.1.0b1

Note: Visual Scripting has been introduced in 2021.1.0b1

Environment: Windows 10, Mac 11.0