TypeError: Cannot convert undefined or null to object

## Error

```
Cannot convert undefined or null to object
```

## Stack trace

```
../app/javascript/components/track/exercise-community-solutions-list/exercise-tag-filter/ExerciseTagFilter.tsx:11 in ExerciseTagFilter
div
div
div
../app/javascript/components/track/ExerciseCommunitySolutionsList.tsx:44 in ExerciseCommunitySolutionsList
Suspense
../node_modules/@sentry/react/src/errorboundary.tsx:101 in new ErrorBoundary
../node_modules/@tanstack/react-query/src/QueryClientProvider.tsx:30 in QueryClientProvider
```

## Tracking Details
- **Project**: exercism-js
- **Sentry**: [TypeError: Cannot convert undefined or null to object](https://thalamus-ai.sentry.io/issues/141784203/)
- **Culprit**: Object.keys()
- **First seen:** Aug 20, 2026

Start at app/javascript/components/track/exercise-community-solutions-list/exercise-tag-filter/ExerciseTagFilter.tsx:11 and inspect the value passed to Object.keys. Reproduce the exercism-js community-solutions view that triggers the Sentry error, then verify the component no longer throws when that value is undefined or null.

Written by the indexing model from the issue text.