Welcome screen is squishy when video turned off

### Steps to reproduce

1. Alt+Left arrow key (on Windows) to put Element Call on the left side of your monitor
2. UI is relatively fine with video
3. Turn off video
4. Squish

### Outcome

#### What did you expect?

UI to not squish going from video to not-video.

#### What happened instead?

### Operating system

Windows

### Browser information

Chrome

### URL for webapp

call.element.io (pro)

### Will you send logs?

No

Reproduce the issue at call.element.io in Chrome on Windows by narrowing the window with Alt+Left, then toggling video off and comparing the welcome screen layout. Trace the welcome screen and video-toggle layout entry points until the squishing behavior is located; done means the UI keeps an usable layout when video is turned off.

Written by the indexing model from the issue text.