FULL PRODUCT VERSION :
java version "1.8.0_131"
Java(TM) SE Runtime Environment (build 1.8.0_131-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.131-b11, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [version 10.0.15063]

A DESCRIPTION OF THE PROBLEM :
This is an upstream bug for:
https://josm.openstreetmap.de/ticket/14795

As per quality outreach please add label "josm-found" to this bug report.

On Windows 10, a JFileChooser can fails to be initialized with the following stacktrace:

java.lang.NullPointerException
at sun.awt.shell.Win32ShellFolderManager2.createShellFolder(Unknown Source)
at sun.awt.shell.Win32ShellFolderManager2.getRecent(Unknown Source)
at sun.awt.shell.Win32ShellFolderManager2.get(Unknown Source)
at sun.awt.shell.ShellFolder.get(Unknown Source)
at sun.swing.WindowsPlacesBar.<init>(Unknown Source)
at com.sun.java.swing.plaf.windows.WindowsFileChooserUI.updateUseShellFolder(Unknown Source)
at com.sun.java.swing.plaf.windows.WindowsFileChooserUI.installComponents(Unknown Source)
at javax.swing.plaf.basic.BasicFileChooserUI.installUI(Unknown Source)
at com.sun.java.swing.plaf.windows.WindowsFileChooserUI.installUI(Unknown Source)
at javax.swing.JComponent.setUI(Unknown Source)
at javax.swing.JFileChooser.updateUI(Unknown Source)
at javax.swing.JFileChooser.setup(Unknown Source)
at javax.swing.JFileChooser.<init>(Unknown Source)
at javax.swing.JFileChooser.<init>(Unknown Source)

Looking at the source code it seems the most plausible explanation is that an exception occurs in Win32ShellFolderManager2.getDesktop but is silently ignored. Thus getDesktop() returns null:

    static Win32ShellFolder2 getDesktop() {
        if (desktop == null) {
            try {
                desktop = new Win32ShellFolder2(DESKTOP);
            } catch (SecurityException e) {
                // Ignore error
            } catch (IOException e) {
                // Ignore error
            } catch (InterruptedException e) {
                // Ignore error
            }
        }
        return desktop;
    }

And the NPE occurs because of parent (desktop) is null:

    static Win32ShellFolder2 createShellFolder(Win32ShellFolder2 parent, File file)
            throws FileNotFoundException, InterruptedException {
        long pIDL;
        try {
            pIDL = parent.parseDisplayName(file.getCanonicalPath());
        } catch (IOException ex) {
            pIDL = 0;
        }
        if (pIDL == 0) {
            // Shouldn't happen but watch for it anyway
            throw new FileNotFoundException("File " + file.getAbsolutePath() + " not found");
        }

        try {
            return createShellFolderFromRelativePIDL(parent, pIDL);
        } finally {
            Win32ShellFolder2.releasePIDL(pIDL);
        }
    }


ERROR MESSAGES/STACK TRACES THAT OCCUR :
java.lang.NullPointerException
at sun.awt.shell.Win32ShellFolderManager2.createShellFolder(Unknown Source)
at sun.awt.shell.Win32ShellFolderManager2.getRecent(Unknown Source)
at sun.awt.shell.Win32ShellFolderManager2.get(Unknown Source)
at sun.awt.shell.ShellFolder.get(Unknown Source)
at sun.swing.WindowsPlacesBar.<init>(Unknown Source)
at com.sun.java.swing.plaf.windows.WindowsFileChooserUI.updateUseShellFolder(Unknown Source)
at com.sun.java.swing.plaf.windows.WindowsFileChooserUI.installComponents(Unknown Source)
at javax.swing.plaf.basic.BasicFileChooserUI.installUI(Unknown Source)
at com.sun.java.swing.plaf.windows.WindowsFileChooserUI.installUI(Unknown Source)
at javax.swing.JComponent.setUI(Unknown Source)
at javax.swing.JFileChooser.updateUI(Unknown Source)
at javax.swing.JFileChooser.setup(Unknown Source)
at javax.swing.JFileChooser.<init>(Unknown Source)
at javax.swing.JFileChooser.<init>(Unknown Source)

REPRODUCIBILITY :
This bug can be reproduced rarely.