Improves the readability of the backup code a bit

src/main/java/net/knarcraft/minecraftserverlauncher/userinterface/BackupGUI.java

@@ -75,19 +75,19 @@ public class BackupGUI implements ActionListener {
      * Destroys the backup GUI
      */
     public static void destroy() {
-        BackupUtil.abortBackup();
-        progressTextArea = null;
-        progressBar = null;
-        cancelButton = null;
         if (frame != null) {
             frame.dispose();
+            frame = null;
+            progressBar = null;
+            progressTextArea = null;
+            cancelButton = null;
         }
-        frame = null;
     }
 
     @Override
     public void actionPerformed(ActionEvent actionEvent) {
         if (actionEvent.getSource() == cancelButton) {
+            BackupUtil.abortBackup();
             destroy();
         }
     }