Drawing to Graphics2D / ScratchFileBuffer not closed

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.io.File;
import java.io.IOException;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;

public class PanelTest {
   
    private static JPanel getTestPanel() {
        PDDocument doc = null;
        try {
            doc = PDDocument.load(new File("anyfile.pdf"));
        } catch (IOException e) {
            e.printStackTrace();
        }
        final PDFRenderer renderer = new PDFRenderer(doc);
        JPanel panel = new JPanel() {
            @Override
            protected void paintComponent(Graphics g) {
                try {
                    renderer.renderPageToGraphics(0, (Graphics2D) g, 0.5f);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        };
        return panel;
    }

    public static void main(String[] args) throws Exception {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
                frame.add(getTestPanel());
                frame.pack();
                frame.setSize(600, 400);
                Dimension paneSize = frame.getSize();
                Dimension screenSize = frame.getToolkit().getScreenSize();
                frame.setLocation((screenSize.width - paneSize.width) / 2, (screenSize.height - paneSize.height) / 2);
                frame.setTitle("Test");
                frame.setVisible(true);
            }
        });
    }
}