Tiles near the bottom of the window in grid mode become un-clickable half way down.

### Steps to reproduce

1. Participate in a call in Grid mode
2. Resize the window if necessary to have tiles scrollable underneath the controls

### Outcome

#### What did you expect?

- Tiles not directly underneath the controls should be clickable.
- Tiles directly underneath the controls should be clickable outside the bounds of the control buttons.

#### What happened instead?

There appears to be an invisible bar housing the controls that swallows up the mouse focus.

https://github.com/vector-im/element-call/assets/6060466/ee25753b-9b65-469b-a1d4-08c43fa81689

### Operating system

macOS

### Browser information

Firefox & Safari.

### URL for webapp

call.element.io

### Will you send logs?

No

Reproduce the issue in Grid mode on call.element.io using Firefox or Safari, resizing the window so tiles scroll beneath the controls. Trace the tile and control overlay behavior in the TypeScript frontend; done means visible tiles remain clickable and tiles beneath the controls are clickable outside the buttons.

Written by the indexing model from the issue text.