Issue #3266193 by Chalk, Liam Morland: Warning: DOMNode::appendChild(): Document Fragment is empty

src/TocBuilder.php

@@ -113,7 +113,9 @@ class TocBuilder implements TocBuilderInterface {
       ];
       $fragment_node = $dom->createDocumentFragment();
       $fragment_node->appendXML($this->renderer->render($build));
-      $dom->getElementsByTagName('body')->item(0)->appendChild($fragment_node);
+      if (!empty($fragment_node->textContent)) {
+        $dom->getElementsByTagName('body')->item(0)->appendChild($fragment_node);
+      }
     }
 
     return Html::serialize($dom);