title: Mobx-state-tree Clone also changes the original item?
body: <p>I have the following model snippet:</p>
  
  <pre><code>nodeOrigin: types.maybe(types.reference(nodeState)),
  node: types.maybe(nodeState),
  </code></pre>
  
  <p>And I start editing a node by the following function (the original node i saved so it can be used in a undo() function):</p>
  
  <pre><code>startEditing(node) {
      self.nodeOrigin = node;
      self.node = clone(node);
  }
  </code></pre>
  
  <p>And in my render method the editing node is used like this:</p>
  
  <pre><code>&lt;form className="form"&gt;
       &lt;TextField margin='dense' value={getStore().node["name"]} /&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>But when I change the name and print the content of both the node and the original node, they have both the changed name. NodeOriginal should contain the original name. What am I doing wrong?</p>