crash when starting routing helper, after downloading incomplete members for relation

[Polyglot]

What steps will reproduce the problem?

What is the expected result?

What happens instead?

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

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2018-08-06 00:26:16 +0200 (Mon, 06 Aug 2018)
Build-Date:2018-08-06 01:52:55
Revision:14100
Relative:URL: ^/trunk

Identification: JOSM/1.5 (14100 en) Linux Mint 18.3 Sylvia
Memory Usage: 1489 MB / 2711 MB (447 MB allocated, but free)
Java version: 1.8.0_171-8u171-b11-0ubuntu0.16.04.1-b11, Oracle Corporation, OpenJDK 64-Bit Server VM
Screen: :0.0 1600x900
Maximum Screen Size: 1600x900
Java package: openjdk-8-jre:amd64-8u171-b11-0ubuntu0.16.04.1
Dataset consistency test: No problems found

Plugins:
+ Mapillary (v1.5.15)
+ OpeningHoursEditor (34389)
+ apache-commons (34389)
+ apache-http (34389)
+ buildings_tools (34212)
+ ejml (34389)
+ geotools (34125)
+ jts (34206)
+ measurement (34206)
+ opendata (34389)
+ pt_assistant (306)
+ reverter (34271)
+ scripting (30785)
+ tag2link (34109)
+ terracer (34109)
+ todo (30305)
+ utilsplugin2 (34389)

Tagging presets:
+ https://josm.openstreetmap.de/josmfile?page=Presets/BENELUX&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/Trees&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/OneClick&zip=1

Map paint styles:
+ https://josm.openstreetmap.de/josmfile?page=Styles/PublicTransport&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/NumberedCycleNodeNetworks&zip=1

Last errors/warnings:
- E: java.net.UnknownHostException: api.openstreetmap.org
- E: java.util.concurrent.ExecutionException: org.openstreetmap.josm.io.OsmTransferException: Could not connect to the OSM server. Please check your internet connection.. Cause: org.openstreetmap.josm.io.OsmTransferException: Could not connect to the OSM server. Please check your internet connection.. Cause: java.net.UnknownHostException: api.openstreetmap.org
- W: java.net.UnknownHostException: api.openstreetmap.org
- W: Already here java.net.UnknownHostException: api.openstreetmap.org
- E: java.net.UnknownHostException: api.openstreetmap.org
- E: java.util.concurrent.ExecutionException: org.openstreetmap.josm.io.OsmTransferException: Could not connect to the OSM server. Please check your internet connection.. Cause: org.openstreetmap.josm.io.OsmTransferException: Could not connect to the OSM server. Please check your internet connection.. Cause: java.net.UnknownHostException: api.openstreetmap.org
- W: java.net.UnknownHostException: api.openstreetmap.org
- E: java.net.UnknownHostException: api.openstreetmap.org
- W: org.openstreetmap.josm.io.OsmTransferException: Could not connect to the OSM server. Please check your internet connection.. Cause: java.net.UnknownHostException: api.openstreetmap.org
- E: Handled by bug report queue: java.lang.IndexOutOfBoundsException: Index: 0, Size: 0


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

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: AWT-EventQueue-0 (18) of main
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
	at java.util.ArrayList.rangeCheck(ArrayList.java:657)
	at java.util.ArrayList.get(ArrayList.java:433)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction.downloadEntireArea(MendRelationAction.java:251)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction.initialise(MendRelationAction.java:235)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction.actionPerformed(MendRelationAction.java:212)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
	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:6533)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
	at java.awt.Component.processEvent(Component.java:6298)
	at java.awt.Container.processEvent(Container.java:2238)
	at java.awt.Component.dispatchEventImpl(Component.java:4889)
	at java.awt.Container.dispatchEventImpl(Container.java:2296)
	at java.awt.Component.dispatchEvent(Component.java:4711)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4897)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4534)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4475)
	at java.awt.Container.dispatchEventImpl(Container.java:2282)
	at java.awt.Window.dispatchEventImpl(Window.java:2746)
	at java.awt.Component.dispatchEvent(Component.java:4711)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:760)
	at java.awt.EventQueue.access$500(EventQueue.java:97)
	at java.awt.EventQueue$3.run(EventQueue.java:709)
	at java.awt.EventQueue$3.run(EventQueue.java:703)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:90)
	at java.awt.EventQueue$4.run(EventQueue.java:733)
	at java.awt.EventQueue$4.run(EventQueue.java:731)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:730)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)