title: Firebase Invalid document reference. Document references must have an even number of segments
body: <p>What is wrong with this query? </p>
  
  <pre><code>const db = firebase.firestore()
  const query = db.doc(this.props.user.uid).collection('statements').orderBy('uploadedOn', 'desc').limit(50)
  </code></pre>
  
  <p>I get the following error: </p>
  
  <pre><code>Uncaught Error: Invalid document reference. Document references must have an even number of segments, but FrMd6Wqch8XJm32HihF14tl6Wui2 has 1
      at new FirestoreError (index.cjs.js:346)
      at Function.DocumentReference.forPath (index.cjs.js:15563)
      at Firestore.doc (index.cjs.js:15368)
      at UploadStatementPresentation.componentWillMount (UploadStatementPage.jsx:61)
      at UploadStatementPresentation.componentWillMount (createPrototypeProxy.js:44)
      at callComponentWillMount (react-dom.development.js:6872)
      at mountClassInstance (react-dom.development.js:6968)
      at updateClassComponent (react-dom.development.js:8337)
      at beginWork (react-dom.development.js:8982)
      at performUnitOfWork (react-dom.development.js:11814)
  </code></pre>