message: fix error bag signature
diff: @@ -187,7 +187,7 @@ export default class ErrorBag {
  /**
  * Gets the first error message for a specific field that not match the rule.
  */
  - firstNot (name: string, rule: string, scope?: string | null = null) {
  + firstNot (name: string, rule?: string = 'required', scope?: string | null = null) {
  const error = this.collect(name, scope, false).filter(e => e.rule !== rule)[0];
  return (error && error.msg) || null;
  