JOSM crashes on startup

[barth@…]

What steps will reproduce the problem?

1. Start JOSM

What is the expected result?

JOSM is usable.

What happens instead?

A popup informs me that an unexpected exception occured.

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

I installed JOSM from the archlinux repository. I did not work on first startup.

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2020-02-24 22:06:28 +0100 (Mon, 24 Feb 2020)
Build-Date:2020-02-24 21:08:22
Revision:15927
Relative:URL: ^/trunk

Identification: JOSM/1.5 (15927 en_GB) Linux Arch Linux
Memory Usage: 386 MB / 7127 MB (320 MB allocated, but free)
Java version: 1.8.0_242-b08, Oracle Corporation, OpenJDK 64-Bit Server VM
Screen: :0.0 2560x1440
Maximum Screen Size: 2560x1440
VM arguments: [-Djosm.restart=true]

Last errors/warnings:
- E: Handled by bug report queue: javax.json.stream.JsonParsingException: Unexpected char 60 at (line no=1, column no=1, offset=0)


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

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: main (1)
javax.json.stream.JsonParsingException: Unexpected char 60 at (line no=1, column no=1, offset=0)
	at org.glassfish.json.JsonTokenizer.unexpectedChar(JsonTokenizer.java:601)
	at org.glassfish.json.JsonTokenizer.nextToken(JsonTokenizer.java:418)
	at org.glassfish.json.JsonParserImpl$NoneContext.getNextEvent(JsonParserImpl.java:413)
	at org.glassfish.json.JsonParserImpl.next(JsonParserImpl.java:363)
	at org.openstreetmap.josm.tools.Territories.initializeExternalData(Territories.java:168)
	at org.openstreetmap.josm.tools.Territories.initialize(Territories.java:123)
	at org.openstreetmap.josm.spi.lifecycle.InitializationTask.call(InitializationTask.java:33)
	at org.openstreetmap.josm.spi.lifecycle.Lifecycle.runInitializationTasks(Lifecycle.java:99)
	at org.openstreetmap.josm.spi.lifecycle.Lifecycle.initialize(Lifecycle.java:71)
	at org.openstreetmap.josm.gui.MainApplication.mainJOSM(MainApplication.java:903)
	at org.openstreetmap.josm.gui.MainApplication$3.processArguments(MainApplication.java:276)
	at org.openstreetmap.josm.gui.MainApplication.main(MainApplication.java:703)

[stoecker]

Closed as duplicate of #18772.