UnsupportedOperationException with relations

[naoliv]

Sorted a relation and then clicked OK:

Repository Root: http://josm.openstreetmap.de/svn
Build-Date: 2015-07-06 01:31:55
Last Changed Author: bastiK
Revision: 8574
Repository UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Relative URL: ^/trunk
URL: http://josm.openstreetmap.de/svn/trunk
Last Changed Date: 2015-07-05 22:14:49 +0200 (Sun, 05 Jul 2015)
Last Changed Rev: 8574

Identification: JOSM/1.5 (8574 pt_BR) Linux Debian GNU/Linux unstable (sid)
Memory Usage: 402 MB / 4029 MB (90 MB allocated, but free)
Java version: 1.7.0_79, Oracle Corporation, OpenJDK 64-Bit Server VM
Java package: openjdk-7-jre:amd64-7u79-2.5.5-1
VM arguments: [-Dawt.useSystemAAFontSettings=on]
Dataset consistency test: No problems found

Plugins:
- AddrInterpolation (31241)
- Create_grid_of_ways (31241)
- FastDraw (31265)
- FixAddresses (31241)
- OpeningHoursEditor (31241)
- PicLayer (31241)
- SimplifyArea (31241)
- buildings_tools (31241)
- download_along (31241)
- editgpx (31241)
- geotools (31126)
- graphview (31241)
- jts (31126)
- measurement (31289)
- merge-overlap (31241)
- opendata (31241)
- pdfimport (31241)
- poly (31241)
- reverter (31241)
- tagging-preset-tester (31241)
- todo (29154)
- turnrestrictions (31241)
- undelete (31241)
- utilsplugin2 (31241)

Last errors/warnings:
- E: java.lang.UnsupportedOperationException

java.lang.UnsupportedOperationException
	at java.util.Collections$1.remove(Collections.java:3313)
	at java.util.AbstractCollection.clear(AbstractCollection.java:432)
	at java.util.AbstractMap.clear(AbstractMap.java:288)
	at org.openstreetmap.josm.gui.tagging.TagEditorModel.applyToTags(TagEditorModel.java:421)
	at org.openstreetmap.josm.gui.tagging.TagEditorModel.applyToPrimitive(TagEditorModel.java:410)
	at org.openstreetmap.josm.gui.dialogs.relation.GenericRelationEditor$SavingAction.applyExistingNonConflictingRelation(GenericRelationEditor.java:1310)
	at org.openstreetmap.josm.gui.dialogs.relation.GenericRelationEditor$OKAction.run(GenericRelationEditor.java:1425)
	at org.openstreetmap.josm.gui.dialogs.relation.GenericRelationEditor$OKAction.actionPerformed(GenericRelationEditor.java:1433)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
	at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
	at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:289)
	at java.awt.Component.processMouseEvent(Component.java:6516)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3312)
	at java.awt.Component.processEvent(Component.java:6281)
	at java.awt.Container.processEvent(Container.java:2229)
	at java.awt.Component.dispatchEventImpl(Component.java:4872)
	at java.awt.Container.dispatchEventImpl(Container.java:2287)
	at java.awt.Component.dispatchEvent(Component.java:4698)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
	at java.awt.Container.dispatchEventImpl(Container.java:2273)
	at java.awt.Window.dispatchEventImpl(Window.java:2719)
	at java.awt.Component.dispatchEvent(Component.java:4698)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:747)
	at java.awt.EventQueue.access$300(EventQueue.java:103)
	at java.awt.EventQueue$3.run(EventQueue.java:706)
	at java.awt.EventQueue$3.run(EventQueue.java:704)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
	at java.awt.EventQueue$4.run(EventQueue.java:720)
	at java.awt.EventQueue$4.run(EventQueue.java:718)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:717)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

How to reproduce with the attached file:
Select the relation, edit and change it to type=boundary.

[Don-vip]

Closed as duplicate of #11664.