title: Why inserting a doc result to an array
body: <p>using Apostrophe for tasks purposes, I wonder why <code>self.docs['my-module'].insert(...)</code> result to an array with my element in third position in the callback.</p>
  
  <p>Expected: get the plain object directly.</p>
  
  <p>Steps to reproduce :</p>
  
  <pre><code>// lib/modules/my-module/index.js
  module.exports = {
    construct: (self, options) =&gt; {
      self.apos.modules['apostrophe-tags'].insert({},
        {
          title: 'test'
        },
        {permissions: false},
        (err, doc) =&gt; {
          console.log(doc); // [undefined, undefined, THE_DOC, undefined, undefined]
        }
      );
    }
  };
  </code></pre>
  
  <p><code>console.log</code> show you an array where the data is "in the middle".</p>
  
  <p>My worries behind it is to make safe the way to do : <code>doc[2]</code>. And I'm unable to find why in the source code ...</p>