Unexpected error if GPX layer is the last one closed

[JohnnyGPS]

What steps will reproduce the problem?

1. Open JOSM
2. Open the download dialog
3. select all three sources ("OpenStreetMap data", "Raw GPS data" and "Notes")
4. Click download and wait for everything to be loaded
5. Do your stuff and upload, or skip this step
6. Close first the data layer and any other layers...
7. ...then close the GPX layer

What is the expected result?

The layers get closed and JOSM returns to the "home screen" it started with.

What happens instead?

There is an unexpected exception.

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

URL:http://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2016-11-06 20:18:38 +0100 (Sun, 06 Nov 2016)
Build-Date:2016-11-06 21:45:03
Revision:11223
Relative:URL: ^/trunk

Identification: JOSM/1.5 (11223 en) Windows 7 32-Bit
Memory Usage: 148 MB / 247 MB (33 MB allocated, but free)
Java version: 1.8.0_111-b14, Oracle Corporation, Java HotSpot(TM) Client VM
Screen: \Display0 1680x1050
Maximum Screen Size: 1680x1050
VM arguments: [-Djava.security.manager, -Djava.security.policy=file:<java.home>\lib\security\javaws.policy, -DtrustProxy=true, -Djnlpx.home=<java.home>\bin, -Djnlpx.origFilenameArg=%UserProfile%\AppData\LocalLow\Sun\Java\Deployment\cache\6.0\56\1ee8cfb8-733b7c99, -Djnlpx.remove=false, -Djava.util.Arrays.useLegacyMergeSort=true, -Djnlpx.splashport=63706, -Djnlp.application.href=https://josm.openstreetmap.de/download/josm.jnlp, -Djnlpx.jvm=<java.home>\bin\javaw.exe, -Djnlpx.vmargs=LURqYXZhLnV0aWwuQXJyYXlzLnVzZUxlZ2FjeU1lcmdlU29ydD10cnVlAC1Eam5scC5hcHBsaWNhdGlvbi5ocmVmPWh0dHBzOi8vam9zbS5vcGVuc3RyZWV0bWFwLmRlL2Rvd25sb2FkL2pvc20uam5scAA=]

Plugins:
+ CADTools (1006)
+ Create_grid_of_ways (32699)
+ InfoMode (33004)
+ buildings_tools (33004)
+ contourmerge (1030)
+ gpsblam (33004)
+ graphview (33004)
+ imagery_offset_db (33004)
+ indoorhelper (33088)
+ measurement (33088)
+ terracer (33088)
+ utilsplugin2 (33088)
+ wikipedia (33098)

Map paint styles:
- https://josm.openstreetmap.de/josmfile?page=Styles/Enhanced_Lane_and_Road_Attributes&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Landcover&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Power&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/PublicTransport&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Lane_and_Road_Attributes&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Maxspeed&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Sidewalks&zip=1

Last errors/warnings:
- E: Handled by bug report queue: java.lang.IllegalArgumentException: Listener was not registered before: LayerChangeAdapter [org.openstreetmap.josm.plugins.gpsblam.GPSBlamMode@10f7674]


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

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: AWT-EventQueue-2 (55) of javawsApplicationThreadGroup
java.lang.IllegalArgumentException: Listener was not registered before: LayerChangeAdapter [org.openstreetmap.josm.plugins.gpsblam.GPSBlamMode@10f7674]
	at org.openstreetmap.josm.gui.layer.LayerManager.removeLayerChangeListener(LayerManager.java:390)
	at org.openstreetmap.josm.gui.layer.LayerManager.removeLayerChangeListener(LayerManager.java:378)
	at org.openstreetmap.josm.actions.JosmAction.destroy(JosmAction.java:218)
	at org.openstreetmap.josm.gui.IconToggleButton.destroy(IconToggleButton.java:72)
	at org.openstreetmap.josm.gui.MapFrame.destroy(MapFrame.java:334)
	at org.openstreetmap.josm.gui.MainPanel.updateContent(MainPanel.java:58)
	at org.openstreetmap.josm.gui.MainPanel$1.afterLastLayerRemoved(MainPanel.java:160)
	at org.openstreetmap.josm.gui.layer.MainLayerManager.realRemoveSingleLayer(MainLayerManager.java:270)
	at org.openstreetmap.josm.gui.layer.LayerManager.realRemoveLayer(LayerManager.java:228)
	at org.openstreetmap.josm.gui.layer.LayerManager.lambda$removeLayer$1(LayerManager.java:214)
	at org.openstreetmap.josm.gui.util.GuiHelper.runInEDTAndWaitWithException(GuiHelper.java:138)
	at org.openstreetmap.josm.gui.layer.LayerManager.removeLayer(LayerManager.java:214)
	at org.openstreetmap.josm.gui.dialogs.layer.DeleteLayerAction.actionPerformed(DeleteLayerAction.java:52)
	at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
	at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
	at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
	at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
	at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
	at java.awt.AWTEventMulticaster.mouseReleased(Unknown Source)
	at java.awt.Component.processMouseEvent(Unknown Source)
	at javax.swing.JComponent.processMouseEvent(Unknown Source)
	at java.awt.Component.processEvent(Unknown Source)
	at java.awt.Container.processEvent(Unknown Source)
	at java.awt.Component.dispatchEventImpl(Unknown Source)
	at java.awt.Container.dispatchEventImpl(Unknown Source)
	at java.awt.Component.dispatchEvent(Unknown Source)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
	at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
	at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
	at java.awt.Container.dispatchEventImpl(Unknown Source)
	at java.awt.Window.dispatchEventImpl(Unknown Source)
	at java.awt.Component.dispatchEvent(Unknown Source)
	at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
	at java.awt.EventQueue.access$500(Unknown Source)
	at java.awt.EventQueue$3.run(Unknown Source)
	at java.awt.EventQueue$3.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.awt.EventQueue$4.run(Unknown Source)
	at java.awt.EventQueue$4.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.run(Unknown Source)

[Klumbumbus]

Closed as duplicate of #13345.