message: clone `isComment` when cloneVNode
diff: @@ -84,6 +84,7 @@ export function cloneVNode (vnode: VNode): VNode {
  cloned.ns = vnode.ns
  cloned.isStatic = vnode.isStatic
  cloned.key = vnode.key
  + cloned.isComment = vnode.isComment
  cloned.isCloned = true
  return cloned
  }
  