Can't open other pages after I update something in the database. (Java FX)

Question

Error:

MyJDBC: Connecting jdbc:mysql://localhost:3306/fys?useSSL=false
MyJDBC: Connecting jdbc:mysql://localhost:3306/fys?useSSL=false
MyJDBC: select * from medewerker WHERE username = 'admin'
MyJDBC: select * from medewerker WHERE username = 'Admin'
MyJDBC: select * from medewerker WHERE username = 'admin'
MyJDBC: SELECT username FROM medewerker WHERE id = '1'
MyJDBC: SELECT username FROM medewerker WHERE id = '1'
MyJDBC: SELECT username FROM medewerker WHERE id = '1'
dec 20, 2017 3:16:57 PM javafx.fxml.FXMLLoader$ValueElement processValue
WARNING: Loading FXML document with JavaFX API of version 9 by JavaFX runtime of version 8.0.152
MyJDBC: SELECT username FROM medewerker WHERE id = '1'
MyJDBC: SELECT username FROM medewerker WHERE id = '1'
MyJDBC: SELECT * from medewerker WHERE username = 'admin'
MyJDBC: UPDATE `fys`.`medewerker` SET `username` = 'Admin' WHERE `id` = 1;
MyJDBC: Data base has been closed
javafx.fxml.LoadException: 
/C:/Users/timte/Programmeren/java/HBO/blok1/FastenYourSeatbelts/target/classes/fxml/LostBagage.fxml
java.lang.NullPointerException

Code:

    @FXML
    private void menuButtonSettingsClick(ActionEvent event)
    {
        loadPage("Settings.fxml");
    }

    private void loadPage(String name)
    {
        String fxmlFileLocation = String.format("/fxml/%s", name);

        Parent pane = loadFXMLFile(fxmlFileLocation);

        anchorPane.getChildren().clear();

        anchorPane.getChildren().add(pane);
    }

    public Parent loadFXMLFile(String fxmlFileLocation){
        try
        {
            return FXMLLoader.load(MainApp.class.getResource(fxmlFileLocation));
        }
        catch (IOException ex)
        {
            System.out.println(ex.getClass().getName() + ": " + ex.getMessage());
            return null;
        }
    }

After I update the database I can't open any other page with JavaFX does someone know a fix? My code works when I don't update the database. only after I update the data base it crashes because it gives a nullpointexeption in my anchorpane.