SQL: double nested fields return null values

[astefan]

For a mapping like the following (one nested field - address - inside another nested field - user):

      "user": {
        "type": "nested",
        "properties": {
          "name" : {
            "type" : "text",
            "fields" : {
              "keyword" : {
                "type" : "keyword"
              }
            }
          },
          "address" : {
            "type" : "nested",
            "properties": {
              "city" : {
                "type" : "keyword"
              },
              "country" : {
                "type" : "keyword"
              }
            }
          }
        }
      }

Simply asking for the entire tree returns null values.

SELECT user.address.city FROM test

user.address.city
-----------------
null             
null             
null             
null             

[elasticmachine]

Pinging @elastic/es-ql (Team:QL)

[astefan]

This is a new issue, following changes in #68802 and #67432.