code: public void onUnhandledTrigger(Action3<S, T, Object[]> unhandledTriggerAction) {
          if (unhandledTriggerAction == null) {
              throw new IllegalStateException("unhandledTriggerAction");
          }
          this.unhandledTriggerAction = unhandledTriggerAction;
      }
docs: Override the default behaviour of throwing an exception when an unhandled trigger is fired
  
  @param unhandledTriggerAction An action to call with state, trigger and params when an unhandled trigger is fired