Bug 336684 [JFace] NPE in Tray Dialog
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/TrayDialog.java
* then invokes a help event on that widget.
	 * If the help tray is already open, it closes it and doesn't invoke
	 * any help listener.
	 */
	private void helpPressed() {
		if (getTray() == null) {
			if (getShell() != null) {
				Control c = getShell().getDisplay().getFocusControl();
				while (c != null) {
					if (c.isListening(SWT.Help)) {
						c.notifyListeners(SWT.Help, new Event());
						break;
					}
					c = c.getParent();
				}
			}
		} else {
			closeTray();
		}
	}
	
	/**
	 * Constructs the tray's widgets and displays the tray in this dialog. The
	 * dialog's size will be adjusted to accommodate the tray.
	 * 
	 * @param tray the tray to show in this dialog
	 * @throws IllegalStateException if the dialog already has a tray open
	 * @throws UnsupportedOperationException if the dialog does not support trays,
	 *            for example if it uses a custom layout.
	 */