Null values in graphql 

{
  "data": {
    "allSanityBlog": {
      "nodes": [
        {
          "title": "Javascript for dummies",
          "categories": [
            {
              "title": null
            }
          ]
        }
      ]
    }
  },
  "extensions": {}
}

I tried to clean the cache, but no results :(