Sorting a topics list in user activities wasn't working because the query parameters weren't passed to `findFiltered()` that does the request to the server.
Made the `sortIcon` more resilient to "input" by always converting the value to a string and checking against `"true"`.
Moved `cleanNullQueryParams()` inside `findFiltered` so we're always removing `null` query parameters.
Internal ref - t/127068