Block menu scrollbar causes overlapping / misplacement of those menus

[Pascal-Flores]

This bug only concerns the input and the more inputs sub menus. There are two cases.

• the sub menu is hidden by the category menu's scrollbar :
  

• the sub menu is placed after a blank space that seems to match with the scrollbar :
  

If I go to another browser tab and go back to the makecode tab, or if the editor finishes compiling the code, the sub menus appear correctly. The bug can be reproduced though.
I think this error is due to the scrollbar which appears when the advanced category is expanded.

Steps to reproduce the behavior:
For the first one :

1. Open or create any project in the makecode editor
2. Click on the Input or more Input category in order to reveal the sub menu
3. Expand the "advanced" category
4. Click on the other category (more input if you clicked on input and vice versa)
5. Et voila! The sub menu is partially hidden by the scrollbar

For the second one :

1. Open or create any project in the makecode editor
2. Expand the "advanced" category
3. Click on the Input or more Input category in order to reveal the sub menu
4. Collapse the "advanced" category
5. Click on the other category (more input if you clicked on input and vice versa)
6. Et voila! The sub menu is misplaced

I'm using the latest Ubuntu Chrome version, with a computer's of which screen resolution is 1024x768px