BlockMenu takes up space beyond body element, introducing scroll

[raghubansh]

BlockMenu introduces unnecessary scroll in documents by attaching itself to bottom. Happens only in Firefox.

To Reproduce
Steps to reproduce the behavior:

1. Git clone
2. yarn
3. yarn start

Expected behavior
There should be no extra space beyond the Editor containing element

Version
11.0.7

Desktop (please complete the following information):

• OS: Mac, Linux
• Browser: Firefox only. Chrome, Safari etc are fine.

My analysis is that the initial state in BlockMenu sets both top and bottom as undefined causing this issue. I tried setting top to 0, but styled div ignored 0, lol. I guess the 0 in calculatePosition is also getting ignored, couldn't check or verify it. I changed the default top to 1 and it fixed the issue.