#3398231: Error when <br> included in allowed tags

src/TocBuilder.php

@@ -86,7 +86,12 @@ class TocBuilder implements TocBuilderInterface {
       ];
 
       $fragment_node = $dom->createDocumentFragment();
-      $fragment_node->appendXML($this->renderer->render($build));
+
+      $header = Html::load($this->renderer->renderPlain($build));
+      foreach ($header->getElementsByTagName('body')->item(0)->childNodes as $node) {
+        $node = $dom->importNode($node, true);
+        $fragment_node->appendChild($node);
+      }
 
       // Replace the header node.
       $replace = TRUE;
@@ -112,7 +117,7 @@ class TocBuilder implements TocBuilderInterface {
         '#item' => NULL,
       ];
       $fragment_node = $dom->createDocumentFragment();
-      $fragment_node->appendXML($this->renderer->render($build));
+      $fragment_node->appendXML($this->renderer->renderPlain($build));
       $dom->getElementsByTagName('body')->item(0)->appendChild($fragment_node);
     }