Error dialog appears, and app refuses to quit

[Alf]

What steps will reproduce the problem?

1. Open JOSM by dragging a gpx file to its icon
2. Set background imagery to ACTMapi April 2020

What is the expected result?

To quit without problems

What happens instead?

When I try to quit, this "unexpected exception" dialog appears. No matter what I do in the app from then on, I can't quit it without using force.

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

System 10.13 High Sierra on the iMac 2017 version

Revision:18004
Build-Date:2021-07-12 00:58:21

Identification: JOSM/1.5 (18004 en_AU) Mac OS X 10.13.6
OS Build number: Mac OS X 10.13.6 (17G9016)
Memory Usage: 708 MB / 4096 MB (362 MB allocated, but free)
Java version: 16.0.1+9, Azul Systems, Inc., OpenJDK 64-Bit Server VM
Look and Feel: com.apple.laf.AquaLookAndFeel
Screen: Display 69973580 2560×1440 (scaling 2.00×2.00)
Maximum Screen Size: 2560×1440
Best cursor sizes: 16×16→16×16, 32×32→32×32
System property file.encoding: UTF-8
System property sun.jnu.encoding: UTF-8
Locale info: en_AU
Numbers with default locale: 1234567890 -> 1234567890
VM arguments: [-Djpackage.app-version=18004, --add-exports=java.base/sun.security.action=ALL-UNNAMED, --add-exports=java.desktop/com.apple.eawt=ALL-UNNAMED, --add-exports=java.desktop/com.sun.imageio.plugins.jpeg=ALL-UNNAMED, --add-exports=java.desktop/com.sun.imageio.spi=ALL-UNNAMED, --add-opens=java.base/java.lang=ALL-UNNAMED, --add-opens=java.base/java.nio=ALL-UNNAMED, --add-opens=java.base/jdk.internal.loader=ALL-UNNAMED, --add-opens=java.base/jdk.internal.ref=ALL-UNNAMED, --add-opens=java.desktop/javax.imageio.spi=ALL-UNNAMED, --add-opens=java.desktop/javax.swing.text.html=ALL-UNNAMED, --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED, -Djpackage.app-path=/Applications/JOSM.app/Contents/MacOS/JOSM]

Plugins:
+ InfoMode (35543)
+ PicLayer (1.0.1)
+ SimplifyArea (35640)
+ apache-commons (35524)
+ buildings_tools (35756)
+ ejml (35458)
+ geotools (35458)
+ importvec (35567)
+ jaxb (35543)
+ jts (35458)
+ measurement (35640)
+ opendata (35640)
+ print (35640)
+ splinex (35718)
+ terracer (35640)
+ undelete (35640)
+ utilsplugin2 (35792)
+ wms-turbo-challenge2 (35562)

Map paint styles:
- https://josm.openstreetmap.de/josmfile?page=Styles/AddressValidator&zip=1
- https://github.com/bastik/mapcss-tools/raw/osm/mapnik2mapcss/osm-results/mapnik.zip

Last errors/warnings:
- 00014.769 E: Failed to locate image 'https://www.spatial.nsw.gov.au/__data/assets/file/0017/224801/favicon.ico'
- 00014.770 E: Failed to locate image 'https://www.spatial.nsw.gov.au/__data/assets/file/0017/224801/favicon.ico'
- 00014.771 E: Failed to locate image 'https://www.spatial.nsw.gov.au/__data/assets/file/0017/224801/favicon.ico'
- 00014.772 E: Failed to locate image 'https://www.spatial.nsw.gov.au/__data/assets/file/0017/224801/favicon.ico'
- 00014.773 E: Failed to locate image 'https://www.spatial.nsw.gov.au/__data/assets/file/0017/224801/favicon.ico'
- 00014.774 E: Failed to locate image 'https://www.spatial.nsw.gov.au/__data/assets/file/0017/224801/favicon.ico'
- 00014.774 E: Failed to locate image 'https://www.spatial.nsw.gov.au/__data/assets/file/0017/224801/favicon.ico'
- 00014.775 E: Failed to locate image 'https://www.spatial.nsw.gov.au/__data/assets/file/0017/224801/favicon.ico'
- 00014.776 E: Failed to locate image 'https://www.spatial.nsw.gov.au/__data/assets/file/0017/224801/favicon.ico'
- 00022.223 E: Handled by bug report queue: java.lang.NullPointerException: Cannot read field "storageFile" because "this.data" is null



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

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: AWT-EventQueue-0 (23) of main
java.lang.NullPointerException: Cannot read field "storageFile" because "this.data" is null
	at org.openstreetmap.josm.gui.layer.GpxLayer.getAssociatedFile(GpxLayer.java:365)
	at org.openstreetmap.josm.actions.SaveAction.updateEnabledState(SaveAction.java:103)
	at org.openstreetmap.josm.actions.JosmAction$LayerChangeAdapter.layerRemoving(JosmAction.java:451)
	at org.openstreetmap.josm.actions.SaveAction$1.layerRemoving(SaveAction.java:89)
	at org.openstreetmap.josm.gui.layer.LayerManager.fireLayerRemoving(LayerManager.java:476)
	at org.openstreetmap.josm.gui.layer.LayerManager.realRemoveSingleLayer(LayerManager.java:278)
	at org.openstreetmap.josm.gui.layer.MainLayerManager.realRemoveSingleLayer(MainLayerManager.java:307)
	at org.openstreetmap.josm.gui.layer.LayerManager.realRemoveLayer(LayerManager.java:266)
	at org.openstreetmap.josm.gui.layer.LayerManager.lambda$removeLayer$1(LayerManager.java:248)
	at org.openstreetmap.josm.gui.util.GuiHelper.runInEDTAndWaitWithException(GuiHelper.java:246)
	at org.openstreetmap.josm.gui.layer.LayerManager.removeLayer(LayerManager.java:248)
	at org.openstreetmap.josm.gui.layer.LayerManager.realResetState(LayerManager.java:515)
	at org.openstreetmap.josm.gui.layer.MainLayerManager.realResetState(MainLayerManager.java:493)
	at org.openstreetmap.josm.gui.util.GuiHelper.runInEDTAndWaitWithException(GuiHelper.java:246)
	at org.openstreetmap.josm.gui.layer.LayerManager.resetState(LayerManager.java:506)
	at org.openstreetmap.josm.gui.MainTermination.run(MainTermination.java:43)
	at org.openstreetmap.josm.spi.lifecycle.Lifecycle.exitJosm(Lifecycle.java:121)
	at org.openstreetmap.josm.gui.MainApplication.exitJosm(MainApplication.java:520)
	at org.openstreetmap.josm.gui.MainApplication$DefaultNativeOsCallback.handleQuitRequest(MainApplication.java:1477)
	at org.openstreetmap.josm.tools.PlatformHookOsx.invoke(PlatformHookOsx.java:185)
	at jdk.proxy2/jdk.proxy2.$Proxy2.handleQuitRequestWith(Unknown Source)
	at java.desktop/com.apple.eawt._AppEventHandler$_QuitDispatcher.performUsing(Unknown Source)
	at java.desktop/com.apple.eawt._AppEventHandler$_QuitDispatcher.performUsing(Unknown Source)
	at java.desktop/com.apple.eawt._AppEventHandler$_AppEventDispatcher$1.run(Unknown Source)
	at java.desktop/java.awt.event.InvocationEvent.dispatch(Unknown Source)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(Unknown Source)
	at java.desktop/java.awt.EventQueue$4.run(Unknown Source)
	at java.desktop/java.awt.EventQueue$4.run(Unknown Source)
	at java.base/java.security.AccessController.doPrivileged(Unknown Source)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.desktop/java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.run(Unknown Source)

[Don-vip]

Closed as duplicate of #21105.