Can't open GPX file in public_transport plugin

[jnk0]

What steps will reproduce the problem?

1. Enable Plugin public_transport
2. Click on Public Transport/ Create Stops from GPX ...
3. Click on Downloads folder

What is the expected result?

The file chooser dialog should show all folders inside home directory and one should navigate into a folder and select a GPX file.

What happens instead?

Only one folder is visible (Downloads) if you choose it, JOSM reports a bug.

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

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2021-04-01 23:17:01 +0200 (Thu, 01 Apr 2021)
Revision:17702
Build-Date:2021-04-01 21:46:03
URL:https://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (17702 en) Linux Freedesktop.org 20.08.6 (Flatpak runtime)
Memory Usage: 684 MB / 7956 MB (365 MB allocated, but free)
Java version: 11.0.8+10, Flathub, OpenJDK 64-Bit Server VM
Look and Feel: javax.swing.plaf.metal.MetalLookAndFeel
Screen: :0.0 1920×1080 (scaling 1.00×1.00)
Maximum Screen Size: 1920×1080
Best cursor sizes: 16×16→16×16, 32×32→32×32
Environment variable LANG: en_GB.UTF-8
System property file.encoding: ANSI_X3.4-1968
System property sun.jnu.encoding: ANSI_X3.4-1968
Desktop environment: GNOME

Plugins:
+ pt_assistant (2.1.10-80-g7d9bba3)
+ public_transport (35640)

Map paint styles:
+ https://josm.openstreetmap.de/josmfile?page=Styles/PublicTransport&zip=1

Last errors/warnings:
- 00036.288 E: Handled by bug report queue: java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: ${HOME}/Downloads/Infoblatt Gr��nabfall entsorgen0719.pdf
- 00410.784 E: Handled by bug report queue: java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: ${HOME}/Downloads/Infoblatt Gr��nabfall entsorgen0719.pdf
- 00439.303 E: Handled by bug report queue: java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: ${HOME}/Downloads/Infoblatt Gr��nabfall entsorgen0719.pdf



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

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: Basic L&F File Loading Thread (74)
java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: /home/jsiml/Downloads/Infoblatt Gr��nabfall entsorgen0719.pdf
	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$FilesLoader.run0(BasicDirectoryModel.java:290)
	at java.desktop/javax.swing.plaf.basic.BasicDirectoryModel$FilesLoader.run(BasicDirectoryModel.java:279)
	at java.base/java.lang.Thread.run(Thread.java:834)

[simon04]

Closed as duplicate of #14596.

[simon04]

Flathub ticket: ​https://github.com/flathub/org.openstreetmap.josm/issues/31