title: What is property "displayName" in React? Uncaught TypeError: Cannot read property 'displayName' of null
body: <p>I get the following error and nothing in the error log helps me locate or detect where my mistake is coming from.</p>
  
  <pre><code>Uncaught TypeError: Cannot read property 'displayName' of null
      at getDisplayName (VM12922 backend.js:9159)
      at getDataFiber (VM12922 backend.js:9888)
      at enqueueMount (VM12922 backend.js:10158)
      at mountFiber (VM12922 backend.js:10246)
      at VM12922 backend.js:10306
      at Set.forEach (&lt;anonymous&gt;)
      at Object.walkTree (VM12922 backend.js:10304)
      at VM12922 backend.js:8534
      at &lt;anonymous&gt;:52:32
      at Array.map (&lt;anonymous&gt;)
      at Object.emit (&lt;anonymous&gt;:51:66)
      at setupBackend (VM12922 backend.js:8621)
      at module.exports (VM12922 backend.js:8567)
      at Agent.&lt;anonymous&gt; (VM12922 backend.js:116)
      at Agent.g (VM12922 backend.js:981)
      at Agent.EventEmitter.emit (VM12922 backend.js:894)
      at VM12922 backend.js:302
      at VM12922 backend.js:7619
      at Array.forEach (&lt;anonymous&gt;)
      at VM12922 backend.js:7618
      at Array.forEach (&lt;anonymous&gt;)
      at Bridge._handleMessage (VM12922 backend.js:7611)
      at listener (VM12922 backend.js:92)
  </code></pre>
  
  <p>Because of this error, React devtools wont load to possibly pinpoint the error.</p>
  
  <p>What is this and where do I start. I only have two main components, the code compiles and renders. What does "displayName" refer to?</p>