title: Express next() error
body: <p>I'm working with node+express+MongoDB.</p>
  
  <p>I dont understand this error. 
  When I comment next() it's fine and works but when I use next() I'm getting the error: <p><b>Error: Can't set headers after they are sent.</b><p></p>
  
  <pre><code>videos.route('/')
      .get(function(req, res, next) {
          Video.find({},function (err,videosCollection) {
              if (err)
              {
                  console.log(err);
              }
  
              if(!videosCollection.length)
              {
                  console.log("Videos not found");
              }
              else
              {
                  console.log("videos found");
                  res.status(200).json(videosCollection);
              }
          })
        //  next();
      })
  </code></pre>