`connectStateResults.searchResults` should be of nullable type

## 🐛 Bug description

Currently `searchResults` is of type `SearchResults` but on component initialization using `connectStateResults` HOC, the value is `null` until Algolia's first response. So in reality it's a nullable prop and should be of type `SearchResults | null`.

Start at the TypeScript definition and entry point for the connectStateResults HOC, then inspect how searchResults is initialized before Algolia's first response. Confirm the current prop type and initialization behavior, and verify that the declared type matches the observed null value using the relevant existing type checks or tests.

Written by the indexing model from the issue text.