为什么这个Angular控制器抛出“错误：未知提供者：nProvider < - n”？

jsFiddle of the code:

jsFile的代码：

<div ng-app="">
    <div ng-controller="FirstCtrl">
        <input type="text" ng-model="data.message" />
        {{data.message + " world"}}
    </div>
</div>

function FirstCtrl($scope) {
    $scope.data = {
        message: "Hello"
    };
}
<div ng-ap