title: Mongo $lookup Query Getting as alias blank
body: <pre><code>db.ticket.aggregate([
    {
      $lookup: {
        from: "crmorder",
        localField: "subOrderId",
        foreignField: "currentStatus",
        as: "comments"
      }
    }
  ])
  </code></pre>
  
  <p>in the result comments field is getting blank why?</p>