fix: make sure data from where clause is complete

[Sekhmet]

Closes: https://github.com/checkpoint-labs/checkpoint/issues/258

This PR fixes two issues:

• When querying non-nullable nested field in where prevents crash.
• When using nested where resolve objects and lists of scalars.

Test plan

Run query like this on sx-api:

{
  votes(where: {space_: {}}) {
    space {
      id
      metadata {
        id
        name
        executors
      }
    }
  }
}

[bonustrack]

@solimander Does this PR fix the issue you get?

[solimander]

@solimander Does this PR fix the issue you get?

Yes, looks like that solves it! 🙏