Rules with invalid regex created an "Internal Server Error" in web-ui

- [x] I am on the [latest](https://github.com/ActivityWatch/activitywatch/releases/latest) ActivityWatch version.
- [x] I have searched the issues of this repo and believe that this is not a duplicate.

- **OS name and version**: Any
- **ActivityWatch version**: 0.10

## Describe the bug
Having a rule with an invalid regex will fail queries in "Activities" view which can be confusing.

See following forum topic:
https://forum.activitywatch.net/t/internal-server-error-on-activity-tab/1171/3

## To Reproduce
1. Go to web-ui
2. Create a new category
3. Set the regex rule to a bad regex (such as "notepad++", two + after another is not valid regex)
4. Go to activities view
5. Get an "Internal Server Error"

## Expected behavior
Get a human readable error