NullPointerException using <tab> on exit dialog

[malenki]

What steps will reproduce the problem?

1. start JOSM
2. press ctrl-n for new data layer
3. double click for a new node (any modification should do)
4. press alt+F4
5. when the exit dialog shows up, press <tab>

What is the expected result?

an other button get active

What happens instead?

Exception

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

tested with:
blank ~/.josm
r8952
java -version
openjdk version "1.8.0_66-internal"
OpenJDK Runtime Environment (build 1.8.0_66-internal-b01)
OpenJDK 64-Bit Server VM (build 25.66-b01, mixed mode)

Revision: 8952
Repository Root: http://josm.openstreetmap.de/svn
Relative URL: ^/trunk
Last Changed Author: Don-vip
Last Changed Date: 2015-10-27 14:03:41 +0100 (Tue, 27 Oct 2015)
Build-Date: 2015-10-27 13:05:26
URL: http://josm.openstreetmap.de/svn/trunk
Repository UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last Changed Rev: 8952

Identification: JOSM/1.5 (8952 de) Linux LMDE 2 Betsy
Memory Usage: 395 MB / 2222 MB (297 MB allocated, but free)
Java version: 1.8.0_66-internal, Oracle Corporation, OpenJDK 64-Bit Server VM
VM arguments: [-Dsun.java2d.opengl=false]
Dataset consistency test: No problems found


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

java.lang.NullPointerException
	at org.openstreetmap.josm.gui.io.SaveLayersTableColumnModel$RecommendedActionsTableCell.getTableCellRendererComponent(SaveLayersTableColumnModel.java:43)
	at javax.swing.JTable$AccessibleJTable.getAccessibleChild(JTable.java:7031)
	at javax.swing.JTable$AccessibleJTable.getAccessibleAt(JTable.java:7418)
	at javax.swing.JTable$AccessibleJTable.valueChanged(JTable.java:6933)
	at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:184)
	at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:164)
	at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:211)
	at javax.swing.DefaultListSelectionModel.changeSelection(DefaultListSelectionModel.java:405)
	at javax.swing.DefaultListSelectionModel.changeSelection(DefaultListSelectionModel.java:415)
	at javax.swing.DefaultListSelectionModel.setSelectionInterval(DefaultListSelectionModel.java:459)
	at javax.swing.JTable.changeSelectionModel(JTable.java:2389)
	at javax.swing.JTable.changeSelection(JTable.java:2456)
	at javax.swing.plaf.basic.BasicTableUI$Actions.actionPerformed(BasicTableUI.java:588)
	at javax.swing.SwingUtilities.notifyAction(SwingUtilities.java:1663)
	at javax.swing.JComponent.processKeyBinding(JComponent.java:2882)
	at javax.swing.JTable.processKeyBinding(JTable.java:5259)
	at javax.swing.JComponent.processKeyBindings(JComponent.java:2943)
	at javax.swing.JComponent.processKeyEvent(JComponent.java:2845)
	at java.awt.Component.processEvent(Component.java:6312)
	at java.awt.Container.processEvent(Container.java:2236)
	at java.awt.Component.dispatchEventImpl(Component.java:4891)
	at java.awt.Container.dispatchEventImpl(Container.java:2294)
	at java.awt.Component.dispatchEvent(Component.java:4713)
	at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1954)
	at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:806)
	at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:1074)
	at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:945)
	at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:771)
	at java.awt.Component.dispatchEventImpl(Component.java:4762)
	at java.awt.Container.dispatchEventImpl(Container.java:2294)
	at java.awt.Window.dispatchEventImpl(Window.java:2750)
	at java.awt.Component.dispatchEvent(Component.java:4713)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
	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:76)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
	at java.awt.EventQueue$4.run(EventQueue.java:731)
	at java.awt.EventQueue$4.run(EventQueue.java:729)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
	at org.GNOME.Accessibility.AtkWrapper$4.dispatchEvent(AtkWrapper.java:571)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:109)
	at java.awt.WaitDispatchSupport$2.run(WaitDispatchSupport.java:184)
	at java.awt.WaitDispatchSupport$4.run(WaitDispatchSupport.java:229)
	at java.awt.WaitDispatchSupport$4.run(WaitDispatchSupport.java:227)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.awt.WaitDispatchSupport.enter(WaitDispatchSupport.java:227)
	at java.awt.Dialog.show(Dialog.java:1084)
	at java.awt.Component.show(Component.java:1673)
	at java.awt.Component.setVisible(Component.java:1625)
	at java.awt.Window.setVisible(Window.java:1014)
	at java.awt.Dialog.setVisible(Dialog.java:1005)
	at org.openstreetmap.josm.Main.saveUnsavedModifications(Main.java:1046)
	at org.openstreetmap.josm.Main.saveUnsavedModifications(Main.java:1015)
	at org.openstreetmap.josm.Main.exitJosm(Main.java:1066)
	at org.openstreetmap.josm.gui.MainApplication$1.windowClosing(MainApplication.java:111)
	at java.awt.AWTEventMulticaster.windowClosing(AWTEventMulticaster.java:349)
	at java.awt.AWTEventMulticaster.windowClosing(AWTEventMulticaster.java:349)
	at java.awt.AWTEventMulticaster.windowClosing(AWTEventMulticaster.java:349)
	at java.awt.Window.processWindowEvent(Window.java:2058)
	at javax.swing.JFrame.processWindowEvent(JFrame.java:305)
	at java.awt.Window.processEvent(Window.java:2017)
	at java.awt.Component.dispatchEventImpl(Component.java:4891)
	at java.awt.Container.dispatchEventImpl(Container.java:2294)
	at java.awt.Window.dispatchEventImpl(Window.java:2750)
	at java.awt.Component.dispatchEvent(Component.java:4713)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
...<snip>...

[Don-vip]

In 8960/josm:

fix #12018 - NPE