title: onCall cloud function returns 'Data cannot be encoded in JSON. NAN'
body: <p>I have an onCall function that looks like this..</p>
  <pre><code>exports.getResults = functions.https.onCall((data, context) =&gt; {
    const admin = context.auth.token.admin
    const uniqueId = context.auth.uid
    const doc = db.collection('collection').doc(data.docId)
  
      return doc
        .get()
        .then(querySnapshot =&gt; {
          return querySnapshot.docs.map(doc =&gt; {
            const doc = doc.data()
            const collectionDoc = {
              docValues
            }
      
            return collectionDoc
          })
        })
        
  </code></pre>
  <p>my console.log prints the doc I am requesting as an object, so I'm not sure what the issue is?</p>