[bug] White void behind app when you scroll up or down

[Zorlin]

Describe the bug
If you use a trackpad like on a MacBook you can two-finger move the page and "debounce"/overscroll, which is good - and we don't want to change that - but you expose the white blank void behind the page ;)

To Reproduce
Steps to reproduce the behavior:

1. Launch Orbiter (on the ui-update branch)
2. Two finger scroll
3. See white background appear

Expected behavior
The background design chosen by the lens host should cover the whole background or we should separately call the same colour/background.

Screenshots
Hard to do while moving the mouse sorry :(

Additional context
Probably easy enough for me to even try fixing!