angularjs-ng-show - 長さ 0 の文字列 "" に対して ng-show を機能させる

Question

長さ 0 の文字列 '' に対して ng-show を機能させる方法はありますか?

angular.module('app', []).controller('app', appController);
function appController($scope) {
  $scope.zero = '';
  $scope.string = 'string';
  $scope.n = null;
}

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>
<div ng-app="app" ng-controller="app">
  <div ng-show="zero">MAKE THIS APPEAR</div>
  <div ng-show="string">This appears, as usual</div>
  <div ng-show="n">This should not appear, as usual</div>
</div>