title: Are controller nodes always null inside setOnCloseRequest?
body: <p>I have the following code:</p>
  
  <pre><code>public class Main extends Application {
  
      @FXML
      private Button button;
  
      @Override
      public void start(Stage primaryStage) {
          try {
              ...
  
              primaryStage.setOnCloseRequest(new EventHandler&lt;WindowEvent&gt;() {
  
                  @Override
                  public void handle(WindowEvent event) {
                      System.out.println(button)
                  }
  
              });
  
              ...
      }
  
      @FXML
      private void initialize() {
          System.out.println(button);
      }
  
  }
  </code></pre>
  
  <p>I run it, then click on the close button, and this is the output:</p>
  
  <pre><code>Button[id=button, styleClass=button]'button'
  null
  </code></pre>
  
  <p>Why is button null when called inside setOnCloseRequest?</p>