Rationalise field access.

src/com/dmdirc/ui/UIAttachDialog.java

@@ -38,9 +38,9 @@ import javax.swing.DefaultListCellRenderer;
 import javax.swing.DefaultListModel;
 import javax.swing.JButton;
 import javax.swing.JDialog;
-import javax.swing.JFrame;
 import javax.swing.JList;
 import javax.swing.JPanel;
+import javax.swing.WindowConstants;
 import javax.swing.event.ListSelectionEvent;
 import javax.swing.event.ListSelectionListener;
 
@@ -113,7 +113,7 @@ public class UIAttachDialog extends JDialog implements ActionListener, ListSelec
 
     /** Displays this dialog. */
     public void display() {
-        setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
+        setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
         pack();
         setVisible(true);
     }