message: revert to use defineReactive
diff: @@ -65,8 +65,8 @@ export default (Vue, options = {}) => {
  // There is a validator but it isn't injected, mark as reactive.
  if (! requested && this.$validator) {
  - Vue.set(this.$validator, 'errors', this.$validator.errors);
  - Vue.set(this.$validator, 'fieldBag', this.$validator.fieldBag);
  + Vue.util.defineReactive(this.$validator, 'errors', this.$validator.errors);
  + Vue.util.defineReactive(this.$validator, 'fieldBag', this.$validator.fieldBag);
  }
  if (! this.$options.computed) {
  