Issue #2905420 by mikey_p, DrupalHack, albert volkman: Fix empty render context

src/TocBuilder.php

@@ -86,7 +86,7 @@ class TocBuilder implements TocBuilderInterface {
       ];
 
       $fragment_node = $dom->createDocumentFragment();
-      $html = Html::normalize($this->renderer->render($build));
+      $html = Html::normalize($this->renderer->renderPlain($build));
       // Trim to ensure the first child is a DOMElement.
       $html = trim($html);
       // Build a new DOMDocument for the HTML.
@@ -124,7 +124,7 @@ class TocBuilder implements TocBuilderInterface {
       ];
 
       $fragment_node = $dom->createDocumentFragment();
-      $html = Html::normalize($this->renderer->render($build));
+      $html = Html::normalize($this->renderer->renderPlain($build));
       // Trim to ensure the first child is a DOMElement.
       $html = trim($html);
       // Build a new DOMDocument for the HTML.
@@ -154,7 +154,7 @@ class TocBuilder implements TocBuilderInterface {
     }
 
     $build = $this->buildToc($toc);
-    return $this->renderer->render($build);
+    return $this->renderer->renderPlain($build);
   }
 
   /**