AssertionError on "Resolve to their versions"

[Aurimas]

What steps will reproduce the problem?

1. Open source:trunk/test/data/regress/12376/multipolygon_hang.osm.bz2​
2. Update modified with Ctrl+Alt+M
3. Select all conflicts in the conflicts list.
4. From context menu choose "Resolve to their versions".

What is the expected result?

All conflicts are resloved.

What happens instead?

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: 2016-01-16 03:00:56 +0100 (Sat, 16 Jan 2016)
Build-Date:2016-01-16 02:34:12
Revision:9480
Relative:URL: ^/trunk

Identification: JOSM/1.5 (9480 lt) Linux Ubuntu Xenial Xerus (development branch)
Memory Usage: 607 MB / 3504 MB (400 MB allocated, but free)
Java version: 1.7.0_91-b02, Oracle Corporation, OpenJDK 64-Bit Server VM
Java package: openjdk-7-jre:amd64-7u91-2.6.3-3
VM arguments: [-Djosm.restart=true, -Djosm.home=/home/aurimas/.josm-latest, -Djava.net.useSystemProxies=true]
Dataset consistency test: No problems found

Plugins:
- Mapillary (31976)
- apache-commons (31895)
- apache-http (31895)
- buildings_tools (31895)
- download_along (31772)
- log4j (31895)
- measurement (31895)
- utilsplugin2 (31895)

Last errors/warnings:
- W:  Place and residential area: Could not get presets icon presets/places.png
- E: java.lang.AssertionError
- E: java.lang.AssertionError
- W: Unable to delete archived backup file /home/aurimas/.josm-latest/autosave/deleted_layers/test2.osm_20160115_223927904.osm
- E: java.lang.AssertionError

java.lang.AssertionError
	at org.openstreetmap.josm.gui.conflict.pair.ConflictResolver.decideRemaining(ConflictResolver.java:360)
	at org.openstreetmap.josm.gui.dialogs.ConflictDialog$ResolveToAction.actionPerformed(ConflictDialog.java:532)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
	at javax.swing.AbstractButton.doClick(AbstractButton.java:376)
	at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:833)
	at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:877)
	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$3.run(EventQueue.java:704)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:77)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:87)
	at java.awt.EventQueue$4.run(EventQueue.java:720)
	at java.awt.EventQueue$4.run(EventQueue.java:718)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:77)
	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)

[simon04]

In 9482/josm:

see #12338 fix #12381 - AssertionError on "Resolve to their versions"