fix: host checking

application/source/dom/updater.mjs

@@ -545,12 +545,15 @@ function internalTemplateLookUp(container, key, ref, path) {
 
     const rootNode = container.getRootNode();
     if (rootNode instanceof ShadowRoot) {
-        templateID = rootNode.host.getAttribute(ATTRIBUTE_UPDATER_INSERT_TEMPLATE_ID);
+        const host = rootNode?.host;
+        if (host && host.hasAttribute(ATTRIBUTE_UPDATER_INSERT_TEMPLATE_ID)) {
+            templateID = host.getAttribute(ATTRIBUTE_UPDATER_INSERT_TEMPLATE_ID);
             template = findDocumentTemplate(templateID, container);
             if (template instanceof HTMLTemplateElement) {
                 return template;
             }
         }
+    }
 
     return findDocumentTemplate(templateID, container);
 }