Exception exiting JOSM

[Gerardus Mercator]

The exception reported below was thrown while exiting JOSM:
before exiting, the project was saved manually;
in the exit dialog was chosen NOT to upload data but to save the .osm instead;
after clicking "Perform selected actions", a warning was issued about an exception in a plugin (sorry, don't remember which one...);
After selecting "Update plugin" (even if I believe all the plugins were already updated), the exception below was thrown.

Anyway, TIA for JOSM, a truly great work, and Happy New Year!

URL:http://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2015-11-24 00:04:12 +0100 (Tue, 24 Nov 2015)
Build-Date:2015-11-23 23:14:21
Revision:9060
Relative:URL: ^/trunk

Identification: JOSM/1.5 (9060 en) Windows XP 32-Bit
Memory Usage: 618 MB / 989 MB (67 MB allocated, but free)
Java version: 1.7.0_55, Oracle Corporation, Java HotSpot(TM) Client VM

Plugins:
- DirectDownload (31772)
- ElevationProfile (31772)
- FastDraw (31772)
- FixAddresses (31772)
- HouseNumberTaggingTool (31772)
- ImproveOsm (18)
- InfoMode (31772)
- Mapillary (31802)
- OSMRecPlugin (31772)
- OpeningHoursEditor (31772)
- RoadSigns (31772)
- SeaMapEditor (31772)
- SimplifyArea (31772)
- alignways (31772)
- apache-commons (31772)
- apache-http (31875)
- buildings_tools (31772)
- continuosDownload (1446070193)
- download_along (31772)
- ejml (31772)
- geotools (31774)
- gpsblam (31772)
- gpxfilter (31772)
- imagery-xml-bounds (31772)
- imagery_offset_db (31772)
- imageryadjust (31772)
- jts (31772)
- log4j (31772)
- measurement (31772)
- merge-overlap (31772)
- namemanager (31772)
- openvisible (31772)
- osmarender (31772)
- print (31772)
- proj4j (31772)
- public_transport (31772)
- public_transport_layer (31772)
- rasterfilters (31772)
- reltoolbox (31772)
- reverter (31772)
- rex (1884)
- splinex (31694)
- tageditor (31772)
- tagging-preset-tester (31772)
- terracer (31772)
- tofix (171)
- turnlanes (31772)
- turnrestrictions (31772)
- undelete (31772)
- utilsplugin2 (31772)
- waydownloader (31772)

Last errors/warnings:
- W: JCS - Silent failure during download: http://wms.pcn.minambiente.it/ogc?map=/ms_ogc/WMS_v1.3/raster/ortofoto_colore_12.map&FORMAT=image/png&VERSION=1.1.1&SERVICE=WMS&REQUEST=GetMap&LAYERS=OI.ORTOIMMAGINI.2012&STYLES=&SRS=EPSG:4326&WIDTH=512&HEIGHT=512&BBOX=12.7056802,41.7528775,12.7084268,41.7549265
- W: JCS - Silent failure during download: http://wms.pcn.minambiente.it/ogc?map=/ms_ogc/WMS_v1.3/raster/ortofoto_colore_12.map&FORMAT=image/png&VERSION=1.1.1&SERVICE=WMS&REQUEST=GetMap&LAYERS=OI.ORTOIMMAGINI.2012&STYLES=&SRS=EPSG:4326&WIDTH=512&HEIGHT=512&BBOX=12.7111734,41.7528775,12.7139199,41.7549265
- W: JCS - Silent failure during download: http://wms.pcn.minambiente.it/ogc?map=/ms_ogc/WMS_v1.3/raster/ortofoto_colore_12.map&FORMAT=image/png&VERSION=1.1.1&SERVICE=WMS&REQUEST=GetMap&LAYERS=OI.ORTOIMMAGINI.2012&STYLES=&SRS=EPSG:4326&WIDTH=512&HEIGHT=512&BBOX=12.7084268,41.7528775,12.7111734,41.7549265
- W: JCS - Silent failure during download: http://wms.pcn.minambiente.it/ogc?map=/ms_ogc/WMS_v1.3/raster/ortofoto_colore_12.map&FORMAT=image/png&VERSION=1.1.1&SERVICE=WMS&REQUEST=GetMap&LAYERS=OI.ORTOIMMAGINI.2012&STYLES=&SRS=EPSG:4326&WIDTH=512&HEIGHT=512&BBOX=12.7056802,41.7549265,12.7084268,41.7569754
- E: java.lang.NullPointerException

java.lang.NullPointerException
	at org.openstreetmap.josm.plugins.improveosm.ImproveOsmPlugin.layerRemoved(ImproveOsmPlugin.java:157)
	at org.openstreetmap.josm.gui.MapView.fireLayerRemoved(MapView.java:216)
	at org.openstreetmap.josm.gui.MapView.removeLayer(MapView.java:519)
	at org.openstreetmap.josm.Main.removeLayer(Main.java:531)
	at org.openstreetmap.josm.Main.exitJosm(Main.java:1087)
	at org.openstreetmap.josm.gui.MainApplication$1.windowClosing(MainApplication.java:111)
	at java.awt.AWTEventMulticaster.windowClosing(Unknown Source)
	at java.awt.Window.processWindowEvent(Unknown Source)
	at javax.swing.JFrame.processWindowEvent(Unknown Source)
	at java.awt.Window.processEvent(Unknown Source)
	at java.awt.Component.dispatchEventImpl(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$200(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$1.doIntersectionPrivilege(Unknown Source)
	at java.security.ProtectionDomain$1.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$1.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)

[Don-vip]

Closed as duplicate of #12225.