title: Empty Array left in Mongoose blank object
body: <p>I have a simple Mongoose object:</p>
  
  <pre><code>module.exports = mongoose.model('Flight', new Schema({ 
      name: String,
      nkr: Number,
      outbound: {
          nkr: Number,
          weight: Number,
          facilities: Array,
      }
  });
  </code></pre>
  
  <p>And when I create a new blank flight, I get back data as follows:</p>
  
  <pre><code>"fligts": [{
      "_id": "55e8642d4666a2141019a372",
      "extra" :  {
          "facilities": []
       }
  }]
  </code></pre>
  
  <p>This is inconvenient as if i run <code>flight.outbound.length</code> returns <code>1</code>. I want a black <code>outbound</code> object if nothing is entered, is this possible? </p>