Fix crash on null price range

[orzechdev]

I want to merge this change because... it fixes storefront crashes when the price range is null.

Screenshots

where index.tsx was referenced to

Pull Request Checklist

1. All visible strings are translated with proper context.
2. All data-formatting is locale-aware (dates, numbers, and so on).
3. The changes are tested.
4. The code is documented (docstrings, project documentation).
5. Changes are mentioned in the changelog.

Test Environment Config

API_URI=https://master.staging.saleor.rocks/graphql/

[patrys]

Task linked: CU-7jrvqj Cache issue when I go to the feature branch