fix

Author: patricklx

packages/@glimmer/runtime/lib/vm/element-builder.ts

@@ -256,7 +256,8 @@ export class NewElementBuilder implements ElementBuilder {
 
   private pushModifiers(modifiers: Nullable<ModifierInstance[]>): void {
     this.modifierStack.push(modifiers);
-    if (modifiers && this.env.debugRenderTree) {
+    if (this.env.debugRenderTree) {
+      modifiers = modifiers || []
       const htmlState = {};
       this.htmlElementsState.push(htmlState);
       const shouldAddHtmlElement = modifiers.length || globalThis.ENV_DEBUG_RENDER_TREE_ALL_ELEMENTS