NB editor Null-pointer exception because of javac hints, with non-installed nb-javac plug-in

In NB 11.2 +, with un-installed nb-javac plug-in and enabled Overrides editor hint, whilst editing a Java source file containing Overrides situations, a few seconds later NB raises a red Null-pointer exception notification. Please see attached stacktrace text-file.

How to reproduce the bug, step by step:

1) I use Netbeans Ant projects with JDK11 source-/binary-format, but the bug probably also happens with other project types.

2) When NB asks to install nb-javac plugin, please don't install it. In case it's already installed, un-install it. With enabled nb-javac plugin, the Null-pointer exception bug doesn't happen. (Also the refactoring-rename only works fully with a non-installed nb-javac plug-in.)

3) In NB's menu Tools -> Options -> Editor -> Hints -> Java, in section "Standard javac warnings", enable the Overrides checkbox.

4) Create a simple mini Java source file with offending source code lines, like:

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JCheckBox;
public class Test {
   public static void main(String[] parameter)  {
      JCheckBox jChecker = new JCheckBox();
      jChecker.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent evt) {
         }
      });
   }
}

5) Now whenever we edit some of the code in the source file, a few seconds later, when NB's parser wants to check the source code for potential Overrides hint situations, it raises the red Null-pointer exception notification.

6) Work-around: Disable the Overrides checkbox in the NB editor's hints section.