diff --git a/core/modules/toolbar/src/Menu/ToolbarMenuLinkTree.php b/core/modules/toolbar/src/Menu/ToolbarMenuLinkTree.php
index 4d8c0e0..587b790 100644
--- a/core/modules/toolbar/src/Menu/ToolbarMenuLinkTree.php
+++ b/core/modules/toolbar/src/Menu/ToolbarMenuLinkTree.php
@@ -11,6 +11,9 @@ class ToolbarMenuLinkTree extends MenuLinkTree {
    */
   public function build(array $tree, $level = 0) {
     if ($level == 0) {
+      if (!$tree) {
+        return array();
+      }
       $build = parent::build($tree, $level);
 
       /** @var \Drupal\Core\Menu\MenuLinkInterface $link */