Mongoose的geoNear方法没有返回结果

Question

我在测试API时收到控制台的错误消息。我正在尝试将从geoNear方法返回的结果推送到数组中，但不是返回包含near-by位置文档的数组，而是返回 undefined 。即使我的URL中没有包含坐标的查询字符串，我的API至少应该响应一个空数组。在路上肯定出了什么问题，我真的坚持这个。错误消息如下：

    process.nextTick(function() { throw err; });
                                  ^

TypeError: Cannot read property 'forEach' of undefined
    at C:\Users\Forrest\Desktop\loc8r\app_api\controllers\locations.js:39:10

“Loc”是我的模型的名称，我的控制器看起来像这样

module.exports.locationsListByDistance = function(req, res) {
    var lng = parseFloat(req.query.lng);
    var lat = parseFloat(req.query.lat);
    var point = {
        type: "Point",
        coordinates: [lng, lat]
    };
    var geoOptions = { 
        spherical: true,
        maxDistance: theEarth.getRadsFromDistance(20),
        num: 10
    };
    Loc.geoNear(point, geoOptions, function(err, results, stats) {
        var locations = [];
        results.forEach(function(doc) { // Can't read property 'forEach' of undefined
            locations.push({
                disance: theEarth.getDistanceFromRads(doc.dis),
                name: doc.obj.name,
                address: doc.obj.address,
                rating: doc.obj.rating,
                facilities: doc.obj.facilities,
                _id: doc.obj._id
            });
        });
        sendJsonResponse(res, 200, locations);
    });
};