title: Extending sap.m.List gives me error: ...failed to load 'sap/m/items.js'
body: <p>I tried to extend <code>sap.m.List</code> to a new custom control which i will call <code>MyList</code> here.</p>
  
  <p>Right now my <code>MyList</code> does nothing fancy. Its definition looks like this: </p>
  
  <pre><code>sap.ui.define([
    "sap/m/ListBase"
  ], function (List) {
    "use strict";
    return List.extend("companyname.control.MyList", {
      metadata : {
        defaultAggregation : "items",
        aggregations: {
          items: {type: "sap.ui.core.Control", multiple: true}
        },
      },
      renderer: {}
    });
  });
  </code></pre>
  
  <p>But when i use it with a simple UI5 Control in <code>&lt;items&gt;...&lt;/items&gt;</code>, i get this JavaScript error: </p>
  
  <pre><code>...failed to load 'sap/m/items.js'...
  </code></pre>
  
  <p>This happens when i use a simple Control but not with a ListItem. Even tough i told <code>MyList</code> to accept <code>type: "sap.ui.core.Control"</code> as <code>items</code>.</p>
  
  <p>I think its a lack of understanding how to extend lists. But i cant find any examples for extending <code>sap.m.List</code> on the web.</p>