title: What causes the error "Failed to set the 'currentNode' property on 'TreeWalker'"?
body: <p>While building a WebComponent using Lit-Element and Typescript I got this rather cryptic error message.</p>
  <p>The error occurs when I try to set the <code>checked</code> attribute to an element.</p>
  <p>The culprit is something similar to this:</p>
  <pre class="lang-js prettyprint-override"><code>    return html`&lt;input type=&quot;radio&quot; ${(testValue==0 ? &quot;checked&quot;:&quot;&quot;)}&gt;`
  </code></pre>
  <p>The error message is</p>
  <pre><code>TypeError: Failed to set the 'currentNode' property on 'TreeWalker': The provided value is not of type 'Node'.
  </code></pre>