Program: 36584
Project: 36584
Buggy source:
/** 
 * Initializes the controller class.
 */
private void initialize(){
  getStage().setScene(new Scene(root));
  getStage().getScene().setFill(Color.rgb(0,0,0,0.01));
  getStage().setOpacity(windowOpacity.getValue());
  Rectangle mask=new Rectangle(1,1,BLACK);
  mask.widthProperty().bind(content.widthProperty());
  mask.heightProperty().bind(content.heightProperty());
  content.setClip(mask);
  s.setOnCloseRequest(e -> close());
  s.setFullScreenExitKeyCombination(KeyCombination.NO_MATCH);
  s.addEventHandler(KEY_PRESSED,e -> {
    if (e.getCode() == ESCAPE && isFullscreen()) {
      setFullscreen(false);
      e.consume();
    }
  }
);
  focused.addListener((o,ov,nv) -> root.pseudoClassStateChanged(pcFocused,nv));
  resizing.addListener((o,ov,nv) -> root.pseudoClassStateChanged(pcResized,nv != NONE));
  moving.addListener((o,ov,nv) -> root.pseudoClassStateChanged(pcMoved,nv));
  fullscreen.addListener((o,ov,nv) -> root.pseudoClassStateChanged(pcFullscreen,nv));
  Action.getActions().stream().filter(a -> !a.isGlobal() && a.hasKeysAssigned()).forEach(a -> a.registerInScene(s.getScene()));
  root.addEventFilter(MOUSE_PRESSED,e -> UiContext.setPressedXY(e.getSceneX(),e.getSceneY()));
  root.addEventFilter(MOUSE_CLICKED,e -> UiContext.fireAppMouseClickEvent(this,e));
  header.addEventHandler(DRAG_DETECTED,this::moveStart);
  header.addEventHandler(MOUSE_DRAGGED,this::moveDo);
  header.addEventHandler(MOUSE_RELEASED,this::moveEnd);
  header.setMouseTransparent(false);
  header.setOnMouseClicked(e -> {
    if (e.getButton() == PRIMARY)     if (e.getClickCount() == 2)     toggleMaximize();
    if (e.getButton() == SECONDARY)     if (e.getClickCount() == 2)     setHeaderVisible(!headerVisible);
  }
);
  header_activator.addEventFilter(MOUSE_ENTERED,e -> {
    if (!headerVisible)     applyHeaderVisible(true);
  }
);
  header.addEventFilter(MOUSE_EXITED_TARGET,e -> {
    if (!headerVisible && !moving.get() && resizing.get() == NONE && e.getSceneY() > 20)     applyHeaderVisible(false);
  }
);
  titleL.setMinWidth(0);
  root.setOnScroll(e -> {
    if (e.getDeltaY() > 0)     PLAYBACK.volumeInc();
 else     if (e.getDeltaY() < 0)     PLAYBACK.volumeDec();
  }
);
  root.addEventFilter(KeyEvent.ANY,e -> {
    if (e.getCode().equals(Action.Shortcut_ALTERNATE)) {
      GUI.setLayoutMode(e.getEventType().equals(KEY_PRESSED));
      if (e.getEventType().equals(KEY_PRESSED))       IOPane.drawWidgetIO();
    }
  }
);
  Icon gitB=new Icon(GITHUB,13,Action.get("String_Node_Str"));
  Icon cssB=new Icon(CSS3,13,Action.get("String_Node_Str"));
  Icon iconsB=new Icon(IMAGE,13,Action.get("String_Node_Str"));
  Icon dirB=new Icon(FOLDER,13,Action.get("String_Node_Str"));
  Icon propB=new Icon(GEARS,13,Action.get("String_Node_Str"));
  Icon runB=new Icon(GAVEL,13,Action.get("String_Node_Str"));
  Icon layB=new Icon(COLUMNS,13,Action.get("String_Node_Str"));
  Icon lastFMB=new Icon<>(null,13,"String_Node_Str" + "String_Node_Str",e -> {
    Node b=(Node)e.getSource();
    if (e.getButton() == PRIMARY)     if (LastFM.getScrobblingEnabled())     LastFM.toggleScrobbling();
 else     if (LastFM.isLoginSuccess())     LastFM.toggleScrobbling();
 else     new PopOver("String_Node_Str",LastFM.getLastFMconfig()).show(b);
 else     if (e.getButton() == SECONDARY)     new PopOver("String_Node_Str",LastFM.getLastFMconfig()).show(b);
  }
);
  maintain(LastFM.scrobblingEnabledProperty(),mapB(LASTFM_SQUARE,LASTFM),lastFMB::icon);
  lastFMB.setDisable(true);
  Icon lockB=new Icon(null,13,"String_Node_Str" + "String_Node_Str" + "String_Node_Str",GUI::toggleLayoutLocked);
  maintain(GUI.layoutLockedProperty(),mapB(LOCK,UNLOCK),lockB::icon);
  Icon lmB=new Icon(null,13,Action.get("String_Node_Str"));
  Icon ltB=new Icon(CARET_LEFT,13,"String_Node_Str",() -> ((SwitchPane)getSwitchPane()).alignLeftTab());
  Icon rtB=new Icon(CARET_RIGHT,13,"String_Node_Str",() -> ((SwitchPane)getSwitchPane()).alignRightTab());
  maintain(GUI.layout_mode,mapB(TH,TH_LARGE),lmB::icon);
  Icon guideB=new Icon(GRADUATION_CAP,13,"String_Node_Str",e -> {
    App.guide.resume();
    App.actionStream.push("String_Node_Str");
  }
);
  Icon helpB=createInfoIcon("String_Node_Str" + "String_Node_Str" + "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str");
  leftHeaderBox.getChildren().addAll(gitB,cssB,dirB,iconsB,new Label("String_Node_Str"),layB,propB,runB,lastFMB,new Label("String_Node_Str"),ltB,lockB,lmB,rtB,new Label("String_Node_Str"),guideB,helpB);
  Icon miniB=new Icon(null,13,Action.get("String_Node_Str"));
  maintain(miniB.hoverProperty(),mapB(ANGLE_DOUBLE_UP,ANGLE_UP),miniB::icon);
  Icon ontopB=new Icon(null,13,"String_Node_Str" + "String_Node_Str",this::toggleAlwaysOnTOp);
  maintain(alwaysOnTop,mapB(SQUARE,SQUARE_ALT),ontopB::icon);
  Icon fullscrB=new Icon(null,17,"String_Node_Str" + "String_Node_Str",this::toggleFullscreen);
  maintain(fullscreen,mapB(FULLSCREEN_EXIT,FULLSCREEN),fullscrB::icon);
  Icon minimB=new Icon(WINDOW_MINIMIZE,13,"String_Node_Str",this::toggleMinimize);
  Icon maximB=new Icon(WINDOW_MAXIMIZE,13,"String_Node_Str",this::toggleMaximize);
  Icon closeB=new Icon(CLOSE,13,"String_Node_Str" + "String_Node_Str",this::close);
  rightHeaderBox.getChildren().addAll(miniB,ontopB,fullscrB,minimB,maximB,closeB);
}

Fixed version (ground truth):
/** 
 * Initializes the controller class.
 */
private void initialize(){
  getStage().setScene(new Scene(root));
  getStage().getScene().setFill(Color.rgb(0,0,0,0.01));
  getStage().setOpacity(windowOpacity.getValue());
  Rectangle mask=new Rectangle(1,1,BLACK);
  mask.widthProperty().bind(content.widthProperty());
  mask.heightProperty().bind(content.heightProperty());
  content.setClip(mask);
  s.setOnCloseRequest(e -> close());
  s.setFullScreenExitKeyCombination(KeyCombination.NO_MATCH);
  s.addEventHandler(KEY_PRESSED,e -> {
    if (e.getCode() == ESCAPE && isFullscreen()) {
      setFullscreen(false);
      e.consume();
    }
  }
);
  focused.addListener((o,ov,nv) -> root.pseudoClassStateChanged(pcFocused,nv));
  resizing.addListener((o,ov,nv) -> root.pseudoClassStateChanged(pcResized,nv != NONE));
  moving.addListener((o,ov,nv) -> root.pseudoClassStateChanged(pcMoved,nv));
  fullscreen.addListener((o,ov,nv) -> root.pseudoClassStateChanged(pcFullscreen,nv));
  Action.getActions().stream().filter(a -> !a.isGlobal() && a.hasKeysAssigned()).forEach(a -> a.registerInScene(s.getScene()));
  root.addEventFilter(MOUSE_PRESSED,e -> UiContext.setPressedXY(e.getSceneX(),e.getSceneY()));
  root.addEventFilter(MOUSE_CLICKED,e -> UiContext.fireAppMouseClickEvent(this,e));
  header.addEventHandler(DRAG_DETECTED,this::moveStart);
  header.addEventHandler(MOUSE_DRAGGED,this::moveDo);
  header.addEventHandler(MOUSE_RELEASED,this::moveEnd);
  header.setMouseTransparent(false);
  header.setOnMouseClicked(e -> {
    if (e.getButton() == PRIMARY)     if (e.getClickCount() == 2)     toggleMaximize();
    if (e.getButton() == SECONDARY)     if (e.getClickCount() == 2)     setHeaderVisible(!headerVisible);
  }
);
  header_activator.addEventFilter(MOUSE_ENTERED,e -> {
    if (!headerVisible)     applyHeaderVisible(true);
  }
);
  header.addEventFilter(MOUSE_EXITED_TARGET,e -> {
    if (!headerVisible && !moving.get() && resizing.get() == NONE && e.getSceneY() > 20)     applyHeaderVisible(false);
  }
);
  titleL.setMinWidth(0);
  root.setOnScroll(e -> {
    if (e.getDeltaY() > 0)     PLAYBACK.volumeInc();
 else     if (e.getDeltaY() < 0)     PLAYBACK.volumeDec();
  }
);
  root.addEventFilter(KeyEvent.ANY,e -> {
    if (e.getCode().equals(Action.Shortcut_ALTERNATE)) {
      GUI.setLayoutMode(e.getEventType().equals(KEY_PRESSED));
      if (e.getEventType().equals(KEY_PRESSED))       IOPane.drawWidgetIO();
    }
  }
);
  Icon gitB=new Icon(GITHUB,13,Action.get("String_Node_Str"));
  Icon cssB=new Icon(CSS3,13,Action.get("String_Node_Str"));
  Icon iconsB=new Icon(IMAGE,13,Action.get("String_Node_Str"));
  Icon dirB=new Icon(FOLDER,13,Action.get("String_Node_Str"));
  Icon propB=new Icon(GEARS,13,Action.get("String_Node_Str"));
  Icon runB=new Icon(GAVEL,13,Action.get("String_Node_Str"));
  Icon layB=new Icon(COLUMNS,13,Action.get("String_Node_Str"));
  Icon lastFMB=new Icon<>(null,13,"String_Node_Str" + "String_Node_Str",e -> {
    Node b=(Node)e.getSource();
    if (e.getButton() == PRIMARY)     if (LastFM.getScrobblingEnabled())     LastFM.toggleScrobbling();
 else     if (LastFM.isLoginSuccess())     LastFM.toggleScrobbling();
 else     new PopOver("String_Node_Str",LastFM.getLastFMconfig()).show(b);
 else     if (e.getButton() == SECONDARY)     new PopOver("String_Node_Str",LastFM.getLastFMconfig()).show(b);
  }
);
  maintain(LastFM.scrobblingEnabledProperty(),mapB(LASTFM_SQUARE,LASTFM),lastFMB::icon);
  lastFMB.setDisable(true);
  Icon lockB=new Icon(null,13,"String_Node_Str" + "String_Node_Str" + "String_Node_Str",GUI::toggleLayoutLocked);
  maintain(GUI.layoutLockedProperty(),mapB(LOCK,UNLOCK),lockB::icon);
  Icon lmB=new Icon(null,13,Action.get("String_Node_Str"));
  Icon ltB=new Icon(CARET_LEFT,13,"String_Node_Str",() -> ((SwitchPane)getSwitchPane()).alignLeftTab());
  Icon rtB=new Icon(CARET_RIGHT,13,"String_Node_Str",() -> ((SwitchPane)getSwitchPane()).alignRightTab());
  maintain(GUI.layout_mode,mapB(TH,TH_LARGE),lmB::icon);
  Icon guideB=new Icon(GRADUATION_CAP,13,"String_Node_Str",() -> App.guide.open());
  Icon helpB=createInfoIcon("String_Node_Str" + "String_Node_Str" + "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str");
  leftHeaderBox.getChildren().addAll(gitB,cssB,dirB,iconsB,new Label("String_Node_Str"),layB,propB,runB,lastFMB,new Label("String_Node_Str"),ltB,lockB,lmB,rtB,new Label("String_Node_Str"),guideB,helpB);
  Icon miniB=new Icon(null,13,Action.get("String_Node_Str"));
  maintain(miniB.hoverProperty(),mapB(ANGLE_DOUBLE_UP,ANGLE_UP),miniB::icon);
  Icon ontopB=new Icon(null,13,"String_Node_Str" + "String_Node_Str",this::toggleAlwaysOnTOp);
  maintain(alwaysOnTop,mapB(SQUARE,SQUARE_ALT),ontopB::icon);
  Icon fullscrB=new Icon(null,17,"String_Node_Str" + "String_Node_Str",this::toggleFullscreen);
  maintain(fullscreen,mapB(FULLSCREEN_EXIT,FULLSCREEN),fullscrB::icon);
  Icon minimB=new Icon(WINDOW_MINIMIZE,13,"String_Node_Str",this::toggleMinimize);
  Icon maximB=new Icon(WINDOW_MAXIMIZE,13,"String_Node_Str",this::toggleMaximize);
  Icon closeB=new Icon(CLOSE,13,"String_Node_Str" + "String_Node_Str",this::close);
  rightHeaderBox.getChildren().addAll(miniB,ontopB,fullscrB,minimB,maximB,closeB);
}