Exception on Umlaute in file or folder name

[Helferlein2]

What steps will reproduce the problem?

1. Run JOSM on Linux.
2. In the home directory (here on file system ext4),

• have a file or folder with a name containing an Umlaut (or more), e.g. "Hörbücher"
• or create one, e.g. with "$ touch AäOöUü.umlaute".

3. In JOSM, select File > Open...

What is the expected result?

• The Open dialog with file names appears.

What happens instead?

• For every Umlaut in the name, the popup "You have encountered a bug in JOSM" appears.
• The Open dialog with empty file area is shown.
• InvalidPathException (see below)

Please provide any additional information below. Attach a screenshot if possible.

Notes:

• The Umlaute are correctly shown as such on the console, in KDE's Dolphin and DoubleCommander.
• The file name, put into a file with "$ ll AäOöUü.umlaute > Umlaute.txt" and looked at with a hex editor, appears as "41 C3 A4 4F C3 B6 55 C3 BC 2E 75 6D 6C 61 75 74 65"

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2022-04-04 22:26:00 +0200 (Mon, 04 Apr 2022)
Revision:18427
Build-Date:2022-04-05 01:30:55
URL:https://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (18427 en) Linux Ubuntu 20.04.4 LTS
Memory Usage: 1247 MB / 3928 MB (51 MB allocated, but free)
Java version: 11.0.14.1+1-Ubuntu-0ubuntu1.20.04, Ubuntu, OpenJDK 64-Bit Server VM
Look and Feel: javax.swing.plaf.metal.MetalLookAndFeel
Screen: :0.0 2560×2104 (scaling 1.00×1.00)
Maximum Screen Size: 2560×2104
Best cursor sizes: 16×16→16×16, 32×32→32×32
Environment variable LANG: de_DE.UTF-8
System property file.encoding: ANSI_X3.4-1968
System property sun.jnu.encoding: ANSI_X3.4-1968
Locale info: en_US
Numbers with default locale: 1234567890 -> 1234567890
Desktop environment: KDE
VM arguments: [-Duser.home=${HOME}]

Plugins:
+ OpeningHoursEditor (35924)
+ imagery_offset_db (35893)

Tagging presets:
+ https://github.com/kendzi/Simple3dBuildingsPreset/releases/download/0.9_2018-05-08/s3db-preset.zip

Last errors/warnings:
- 10293.371 E: Handled by bug report queue: java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: /home/j/H��rb��cher
- 10293.383 E: Handled by bug report queue: java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: /home/j/H��rb��cher
- 10412.451 E: Handled by bug report queue: java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: /home/j/H��rb��cher
- 10412.465 E: Handled by bug report queue: java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: /home/j/H��rb��cher
- 10540.558 E: Handled by bug report queue: java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: /home/j/H��rb��cher
- 10540.567 E: Handled by bug report queue: java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: /home/j/H��rb��cher
- 10556.442 E: Handled by bug report queue: java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: /home/j/H��rb��cher
- 10556.454 E: Handled by bug report queue: java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: /home/j/H��rb��cher
- 10665.091 E: Handled by bug report queue: java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: /home/j/A��O��U��.umlaute
- 10665.100 E: Handled by bug report queue: java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: /home/j/A��O��U��.umlaute



=== REPORTED CRASH DATA ===
BugReportExceptionHandler#handleException:
No data collected.

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: Basic L&F File Loading Thread (2330)
java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: /home/j/A��O��U��.umlaute
	at java.base/sun.nio.fs.UnixPath.encode(UnixPath.java:145)
	at java.base/sun.nio.fs.UnixPath.<init>(UnixPath.java:69)
	at java.base/sun.nio.fs.UnixFileSystem.getPath(UnixFileSystem.java:279)
	at java.base/java.nio.file.Path.of(Path.java:147)
	at java.base/java.nio.file.Paths.get(Paths.java:69)
	at java.desktop/sun.awt.shell.ShellFolder.getShellFolder(ShellFolder.java:247)
	at java.desktop/javax.swing.filechooser.FileSystemView.getFiles(FileSystemView.java:523)
	at java.desktop/javax.swing.plaf.basic.BasicDirectoryModel$FilesLoader.run0(BasicDirectoryModel.java:300)
	at java.desktop/javax.swing.plaf.basic.BasicDirectoryModel$FilesLoader.run(BasicDirectoryModel.java:289)
	at java.base/java.lang.Thread.run(Thread.java:829)

[taylor.smock]

Closed as duplicate of #14596.