If inStock: true is added to search, facetValues always return empty

**Describe the bug**
When using the shop API search query with inStock: true, facetValues are always returned as an empty array. Collections are returned, facetValues are not.

**Expected behavior**
It should return facetValues regardless

**Environment (please complete the following information):**
 - @vendure/core version: 3.1.2
 - Nodejs version: 18
 - Database (mysql/postgres etc): mysql