ComboBox remains null from Scene Builder when try to add items

Question

I am stuck in something basic.

A simple comboBox of integers, made from Scene Builder shows null when I try to insert items.

Min Rep Example

Fxml :

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.ComboBox?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.Tab?>
<?import javafx.scene.control.TabPane?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.VBox?>
<?import javafx.scene.text.Font?>
<?import javafx.scene.text.Text?>

<VBox prefHeight="500.0" prefWidth="650.0" xmlns="http://javafx.com/javafx/19" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.Controller">
  <children>
      <AnchorPane prefHeight="500.0" prefWidth="650.0">
         <children>
            <TabPane layoutY="20.0" prefHeight="481.0" prefWidth="650.0" tabClosingPolicy="UNAVAILABLE">
              <tabs>
                <Tab text="File Upload">
                  <content>
                    <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="322.0" prefWidth="654.0">
                           <children>
                              <Button fx:id="fileUpload" layoutX="249.0" layoutY="88.0" mnemonicParsing="false" prefHeight="31.0" prefWidth="139.0" text="Select file to upload" />
                              <Button fx:id="uploadBtn" layoutX="296.0" layoutY="132.0" mnemonicParsing="false" onAction="#onBtnClick" text="Upload" />
                              <Text fx:id="statusMsg" layoutX="285.0" layoutY="186.0" strokeType="OUTSIDE" strokeWidth="0.0" wrappingWidth="78.0" />
                              <Label layoutX="245.0" layoutY="204.0" text="Create Tracks in a file">
                                 <font>
                                    <Font size="18.0" />
                                 </font>
                              </Label>
                              <ComboBox fx:id="tracks" layoutX="197.0" layoutY="247.0" onMouseClicked="#setTrackValue" prefHeight="25.0" prefWidth="89.0" promptText="Tracks" />
                              <Label layoutX="85.0" layoutY="251.0" prefHeight="17.0" prefWidth="103.0" text="Select No of tracks" />
                              <Button fx:id="generateTrackBtn" layoutX="354.0" layoutY="247.0" mnemonicParsing="false" prefHeight="25.0" prefWidth="90.0" text="Generate" />
                           </children>
                        </AnchorPane>
                  </content>
                </Tab>
                <Tab text="Multiwave UI">
                  <content>
                    <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" />
                  </content>
                </Tab>
              </tabs>
            </TabPane>
            <Text fx:id="closeBtn" fontSmoothingType="LCD" layoutX="617.0" layoutY="16.0" onMouseClicked="#closeApp" strokeType="OUTSIDE" strokeWidth="0.0" text="X">
               <font>
                  <Font name="System Bold" size="18.0" />
               </font>
            </Text>
         </children>
      </AnchorPane>
  </children>
</VBox>

Controller:

package application;


import java.net.URL;
import java.util.ResourceBundle;

import javafx.event.ActionEvent;
import javafx.event.Event;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.stage.Stage;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.text.Text;
public class Controller  implements Initializable {
    
    @FXML
    private Button uploadBtn;
    
    @FXML
    private Text closeBtn;
    
    @FXML
    private ComboBox<Integer> tracks;
    
    @FXML
    public void onBtnClick(ActionEvent e) {
        System.out.println("I am clicked");
    }
    
    @FXML
    public void closeApp(Event e)
    {
        Stage s = (Stage) closeBtn.getScene().getWindow();
        s.close();
    }   
    
    @FXML
    public void setTrackValue(ActionEvent e)
    {
        System.out.println("Combobox clicked");
    }

    @Override
    public void initialize(URL arg0, ResourceBundle arg1) {
        
        tracks.getItems().clear(); //This is for trying, whatever I do it returns null
        
    }
    
}

I tried inserting data, clearing items or even seperate action event, all the cases it returns null.

Caused by: java.lang.NullPointerException: Cannot invoke "javafx.scene.control.ComboBox.getItems()" because "this.tracks" is null
    at Multitrack_Waveform_Viewer/application.Controller.initialize(Controller.java:55)
    at javafx.fxml@19/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2655)
    ... 14 more

Main:

package application;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class Main extends Application {
public static void main(String[] args) {
      System.out.println("Running");
    launch(args);
}

@Override
public void start(Stage primaryStage) {
    try {
        System.out.println("Running");
        
            
        Parent root = FXMLLoader.load(getClass().getResource("UI_WaveForm.fxml"));

        primaryStage.setScene(new Scene(root,650,500));
        primaryStage.show();
   
      
    } catch(Exception e) {
        e.printStackTrace();
    }
}

}

Module info:

module Multitrack_Waveform_Viewer {
    requires javafx.controls;
    requires javafx.graphics;
    requires javafx.fxml;
    requires javafx.base;
    
    opens application to javafx.graphics, javafx.fxml;
}

While the other button and close option works fine.

What am I doing wrong here ?

Update:

I reinstalled the JavaFX package and it ran fine. No idea why it happened