title: Mongoose - populate match String in array doesn't work
body: <p>I try to search objects with Mongoose (v4.6.2) using populate. Here are my models (in two different files) : </p>
  
  <pre><code>const experienceSchema = new mongoose.Schema({
    title: { type: String, maxlength: 50 },
    creator: { type: Schema.ObjectId, ref: 'User' },
    creatorName: String,
    city: { type: String, maxlength: 64 },
    interests: [{ type: Schema.ObjectId, ref: 'Interest' }],
  }, { timestamps: true });
  
  const interestSchema = new Schema({
    Name: { type: String, default: '' },
    illustration: { type: String, default: '' },
  }, { timestamps: true });
  </code></pre>
  
  <p>Then I have an array : ["pizza", "GOT"]. So I want to fin all experiences which have at least one interest of the array. So i do this : </p>
  
  <pre><code>experienceModel.find()
  .populate({
       path: 'interests',
       match: { Name: { $in: array }}
  })
  .exec(function(err, exps) {...}
  </code></pre>
  
  <p>Then, I don't know why, the result contains experiences which have no interests, especially those of the array :(</p>
  
  <p>Do you see where the problem could comes from ?</p>
  
  <p>Thank you, have a nice day :)</p>