fix(core): clone mounted hoisted vnodes on patch

...since they may need to be checked as fragment child

packages/runtime-core/src/vnode.ts

@@ -353,6 +353,11 @@ export function normalizeVNode<T, U>(child: VNodeChild<T, U>): VNode<T, U> {
   }
 }
 
+// optimized normalization for template-compiled render fns
+export function cloneIfMounted(child: VNode): VNode {
+  return child.el == null ? child : cloneVNode(child)
+}
+
 export function normalizeChildren(vnode: VNode, children: unknown) {
   let type = 0
   if (children == null) {