message: fix: allow traversing reactive objects which are sealed
diff: @@ -18,7 +18,7 @@ export function traverse (val: any) {
  function _traverse (val: any, seen: SimpleSet) {
  let i, keys
  const isA = Array.isArray(val)
  - if ((!isA && !isObject(val)) || !Object.isExtensible(val)) {
  + if ((!isA && !isObject(val)) || Object.isFrozen(val)) {
  return
  }
  if (val.__ob__) {
  