fix(runtime-core): avoid rendering plainObject as VNode

packages/runtime-core/src/vnode.ts

@@ -793,7 +793,7 @@ export function normalizeVNode(child: VNodeChild): VNode {
       // #3666, avoid reference pollution when reusing vnode
       child.slice(),
     )
-  } else if (typeof child === 'object') {
+  } else if (isVNode(child)) {
     // already vnode, this should be the most common since compiled templates
     // always produce all-vnode children arrays
     return cloneIfMounted(child)