Bug report come if i delet the last member in relation window

[Hanikatu]

What steps will reproduce the problem?

1. select a node of a relation and open the relation window wiht edit
2. select a node on the right side
3. select the last node on the left side
4. klick on the delet button on the right side (not the button with the trash icon)

(hier an example ​https://send.firefox.com/download/2532920d8b15db2f/#r9YiBlWWQdq4TtZRTXbPbQ )

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: 2019-07-10 00:52:47 +0200 (Wed, 10 Jul 2019)
Build-Date:2019-07-10 01:30:51
Revision:15238
Relative:URL: ^/trunk

Identification: JOSM/1.5 (15238 de) Windows 10 64-Bit
OS Build number: Windows 10 Home 1903 (18362)
Memory Usage: 481 MB / 1707 MB (352 MB allocated, but free)
Java version: 1.8.0_221-b11, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Screen: \Display0 1440x900
Maximum Screen Size: 1440x900
Dataset consistency test: No problems found

Last errors/warnings:
- W: No configuration settings found.  Using hardcoded default values for all pools.
- E: Handled by bug report queue: java.lang.IndexOutOfBoundsException: Index: 2, Size: 2


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

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: AWT-EventQueue-0 (17) of main
java.lang.IndexOutOfBoundsException: Index: 2, Size: 2
	at java.util.ArrayList.rangeCheck(ArrayList.java:657)
	at java.util.ArrayList.get(ArrayList.java:433)
	at org.openstreetmap.josm.gui.dialogs.relation.MemberTableModel.getSelectedMembers(MemberTableModel.java:539)
	at org.openstreetmap.josm.gui.dialogs.relation.MemberTableModel.hasIncompleteSelectedMembers(MemberTableModel.java:426)
	at org.openstreetmap.josm.gui.dialogs.relation.actions.DownloadSelectedIncompleteMembersAction.updateEnabledState(DownloadSelectedIncompleteMembersAction.java:46)
	at org.openstreetmap.josm.gui.dialogs.relation.actions.AbstractRelationEditorAction.tableChanged(AbstractRelationEditorAction.java:76)
	at javax.swing.table.AbstractTableModel.fireTableChanged(AbstractTableModel.java:296)
	at javax.swing.table.AbstractTableModel.fireTableDataChanged(AbstractTableModel.java:198)
	at org.openstreetmap.josm.gui.dialogs.relation.MemberTableModel.removeMembersReferringTo(MemberTableModel.java:350)
	at org.openstreetmap.josm.gui.dialogs.relation.actions.RemoveSelectedAction.actionPerformed(RemoveSelectedAction.java:42)
	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:6539)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
	at java.awt.Component.processEvent(Component.java:6304)
	at java.awt.Container.processEvent(Container.java:2239)
	at java.awt.Component.dispatchEventImpl(Component.java:4889)
	at java.awt.Container.dispatchEventImpl(Container.java:2297)
	at java.awt.Component.dispatchEvent(Component.java:4711)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4904)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4535)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4476)
	at java.awt.Container.dispatchEventImpl(Container.java:2283)
	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:74)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:84)
	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:74)
	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)

[Hanikatu]

example