message: remove fallback null after util method update
diff: @@ -30,10 +30,6 @@ export default (options) => ({
  if (!field) return;
  let scope = isObject(value) ? (value.scope || getScope(el)) : getScope(el);
  - if (!scope) {
  - scope = '__global__';
  - }
  -
  field.update({ scope });
  },
  update (el, { expression, value }, { context }) {
  @@ -45,8 +41,8 @@ export default (options) => ({
  field.expression = JSON.stringify(value);
  const scope = isObject(value) ? (value.scope || getScope(el)) : getScope(el);
  field.update({
  - rules: getRules(expression, value, el),
  - scope: scope || '__global__'
  + scope,
  + rules: getRules(expression, value, el)
  });
  },
  unbind (el, { value }, { context }) {
  