TypeError: undefined is not an object (evaluating 'Object.keys(r)')

## Error

```
undefined is not an object (evaluating 'Object.keys(r)')
```

## Stack trace

```
../app/javascript/components/track/exercise-community-solutions-list/exercise-tag-filter/ExerciseTagFilter.tsx:11 in ExerciseTagFilter
../app/javascript/components/track/ExerciseCommunitySolutionsList.tsx:50 in ExerciseCommunitySolutionsList
../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: undefined is not an object (evaluating 'Object.keys(r)')](https://thalamus-ai.sentry.io/issues/142321716/)
- **Culprit**: ExerciseTagFilter(app/javascript/components/track/exercise-community-solutions-list/exercise-tag-filter/ExerciseTagFilter)
- **First seen:** Aug 23, 2026

Start by reading app/javascript/components/track/exercise-community-solutions-list/exercise-tag-filter/ExerciseTagFilter.tsx at line 11, then trace its caller in ExerciseCommunitySolutionsList.tsx at line 50. Reproduce the community-solutions list failure using the Sentry details; done means the list no longer raises the reported TypeError when the relevant value is undefined, with a regression test if the existing test setup supports one.

Written by the indexing model from the issue text.