Fix some of the Serializable interface issues

Author: Eswcvlad

src/main/java/com/itextpdf/rups/io/PdfFileOpenAction.java

@@ -44,12 +44,11 @@ This file is part of the iText (R) project.
 
 import com.itextpdf.rups.RupsConfiguration;
 import com.itextpdf.rups.io.filters.PdfFilter;
-import com.itextpdf.rups.view.Language;
 
 import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
 import java.io.File;
 import java.util.function.Consumer;
-import javax.swing.AbstractAction;
 import javax.swing.JFileChooser;
 import java.awt.Component;
 
@@ -61,7 +60,7 @@ This file is part of the iText (R) project.
  * recently opened file. Will send an open event to the controller.
  * </p>
  */
-public final class PdfFileOpenAction extends AbstractAction {
+public final class PdfFileOpenAction implements ActionListener {
     /**
      * The listener, that is expecting the result of the file chooser action.
      */
@@ -78,7 +77,6 @@ public final class PdfFileOpenAction extends AbstractAction {
      * @param parent   A parent Component for chooser dialog.
      */
     public PdfFileOpenAction(Consumer<File> listener, Component parent) {
-        super(Language.OPEN.getString());
         this.listener = listener;
         this.parent = parent;
     }

src/main/java/com/itextpdf/rups/io/PdfFileSaveAction.java

@@ -45,11 +45,10 @@ This file is part of the iText (R) project.
 import com.itextpdf.rups.RupsConfiguration;
 import com.itextpdf.rups.controller.IRupsController;
 import com.itextpdf.rups.io.filters.PdfFilter;
-import com.itextpdf.rups.view.Language;
 
 import java.awt.Component;
 import java.awt.event.ActionEvent;
-import javax.swing.AbstractAction;
+import java.awt.event.ActionListener;
 import javax.swing.JFileChooser;
 
 /**
@@ -60,7 +59,7 @@ This file is part of the iText (R) project.
  * location with the same name. Will send a save event to the controller.
  * </p>
  */
-public final class PdfFileSaveAction extends AbstractAction {
+public final class PdfFileSaveAction implements ActionListener {
     /**
      * The controller, that is expecting the result of the file chooser action.
      */
@@ -77,7 +76,6 @@ public final class PdfFileSaveAction extends AbstractAction {
      * @param parent     A parent Component for chooser dialog.
      */
     public PdfFileSaveAction(IRupsController controller, Component parent) {
-        super(Language.MENU_BAR_SAVE_AS.getString());
         this.controller = controller;
         this.parent = parent;
     }

src/main/java/com/itextpdf/rups/view/itext/StructureTree.java

@@ -87,7 +87,7 @@ public final class StructureTree extends JTree implements TreeSelectionListener,
      */
     private final PdfReaderController controller;
 
-    private ObjectLoader loader;
+    private transient ObjectLoader loader = null;
 
     private boolean loaded = false;