message: Update deep-assign.ts
diff: @@ -10,7 +10,7 @@ type Object = {
  function assignKey(to: Object, from: Object, key: string) {
  const val = from[key];
  - if (!isDef(val) || (hasOwnProperty.call(to, key) && !isDef(to[key]))) {
  + if (!isDef(val)) {
  return;
  }
  