[16.0] [web_timeline] Selection fields grouping not working

[aribeirogoshawk]

When adding a Selection field to the timeline view, if you try to group by that field, nothing happens.

Module

web_timeline

Describe the bug

When adding a Selection field to the timeline view, if you try to group by that field, nothing happens.

To Reproduce

Affected versions: 16.0

Steps to reproduce the behavior:

1. Add a Selection field to a timeline view
2. Pick that field in the group by section
3. Nothing happens

Expected behavior
A clear and concise description of what you expected to happen.

Additional context
Add any other context about the problem here. (e.g. OS, Python version, ...)