message: fix:the placeholder key in undefined when render async component
diff: @@ -140,7 +140,9 @@ export default {
  // during entering.
  const id: string = `__transition-${this._uid}-`
  child.key = child.key == null
  - ? id + child.tag
  + ? child.isComment
  + ? id + 'comment'
  + : id + child.tag
  : isPrimitive(child.key)
  ? (String(child.key).indexOf(id) === 0 ? child.key : id + child.key)
  : child.key
  