title: "No select item" on JavaFX combobox?
body: <p>What is the correct way to put an item which value is null, inside a ComboBox?
  I tried using <code>myComboBox.getItems().add(null);</code>, and it works, but whenever the user selects this value on the combo box, an exception is thrown on the console:</p>
  
  <pre><code>Exception in thread "JavaFX Application Thread" java.lang.IndexOutOfBoundsException
      at com.sun.javafx.scene.control.ReadOnlyUnbackedObservableList.subList(ReadOnlyUnbackedObservableList.java:136)
  </code></pre>
  
  <p>So i think maybe this is not the correct way of doing that. Any clues?</p>