Admin UI rendering issue when selecting items from long lists

# Bug report

Long lists of items that are checked (ticked) towards the bottom of the window produces a rendering issue in the browser, can't scroll back up to read the top elements when bug is rendered.

Seems to affect Chromium only, test browser `Brave Version 1.26.77 Chromium: 91.0.4472.164 (Official Build) (arm64)`

See video to reproduce:

https://user-images.githubusercontent.com/737821/126092626-ca73a179-48b2-464e-a5a5-d42ac524502b.mov

Start by reproducing the issue shown in the linked video using Brave/Chromium, with a long list and items selected near the bottom. Trace the Admin UI rendering path for that interaction; done means the top elements remain accessible and the list can be scrolled normally after the selection.

Written by the indexing model from the issue text.