NullPointer in PopupMenuContainer caused by JTabbedPane with SCROLL_TAB_LAYOUT

[xescote]

Describe the bug
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException: Cannot invoke "com.github.weisj.darklaf.ui.popupmenu.PopupMenuContainer.adjustSize(java.awt.Dimension, int, int)" because the return value of "com.github.weisj.darklaf.ui.popupmenu.DarkPopupMenuUI.getPopupMenuContainer()" is null
at com.github.weisj.darklaf.ui.popupmenu.DarkPopupMenuUI.getPreferredSize(DarkPopupMenuUI.java:135)
at java.desktop/javax.swing.JComponent.getPreferredSize(JComponent.java:1725)
at com.github.weisj.darklaf.ui.tabbedpane.DarkScrollableTabSupport.actionPerformed(DarkScrollableTabSupport.java:92)
at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1972)
at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2313)
at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)
at com.github.weisj.darklaf.ui.button.DarkButtonListener.mouseReleased(DarkButtonListener.java:72)
at java.desktop/java.awt.Component.processMouseEvent(Component.java:6626)
at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3389)
at java.desktop/java.awt.Component.processEvent(Component.java:6391)

From the code we can see that getPopupMenuContainer() can return null when popupMenu is ScrollPopupMenu
So, when popupMenu is ScrollPopupMenu getPopupMenuContainer always returns null.

private PopupMenuContainer getPopupMenuContainer() {
    if (popupMenuContainer == null && !(popupMenu instanceof ScrollPopupMenu)) {
        popupMenuContainer = new PopupMenuContainer();
    }
    return popupMenuContainer;
}

To Reproduce

This happens when creating many JTabbedPane and they require a popup menu to show.
When click on the popup menu to show the hidden tabs the exception is thrown.

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTabbedPane;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.WindowConstants;


public class BugPopupMenu {
	
	public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, UnsupportedLookAndFeelException
	{
    	UIManager.setLookAndFeel("com.github.weisj.darklaf.DarkLaf");
		JFrame frame = new JFrame();
        SwingUtilities.updateComponentTreeUI(frame);
		JTabbedPane panel = new JTabbedPane();
		panel.setTabLayoutPolicy(JTabbedPane.SCROLL_TAB_LAYOUT);
		for (int idx = 0; idx < 100; idx++)
			panel.addTab("Tab " + idx, new JPanel());
		frame.getContentPane().add(panel);
		frame.setSize(600, 500);
		frame.setVisible(true);
		frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
	}
}

Additional Information:

• OS: [e.g. macOS]
• Darklaf Version: [e.g. 2.7.3]

[weisJ]

This was fixed in d99c8a2, so the next version should resolve this issue.