unexpected exception when adding PDOK imagery

[beyanora@…]

What steps will reproduce the problem?

1. Open JOSM
2. Download bounding box (max lat: 50.8485484, min lon: 5.7080841, max lon: 5.7168818, min lat: 50.8438064) (Maastricht region)
3. Menu > Imagery > PDOK aerial imagery Beeldmateriaal.nl 25cm (WMTS)
4. In the dialog that opens, click "Add layers"

What is the expected result?

Adding an imagery layer to the Layers

What happens instead?

Dialog "An unexpected exception occurred" pops up, directing me here :)

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

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2020-02-26 10:50:27 +0100 (Wed, 26 Feb 2020)
Revision:15937
Build-Date:2020-02-26 09:52:41
URL:https://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (15937 en) Mac OS X 10.15.3
OS Build number: Mac OS X 10.15.3 (19D76)
Memory Usage: 452 MB / 2048 MB (25 MB allocated, but free)
Java version: 11.0.2+9, Oracle Corporation, OpenJDK 64-Bit Server VM
Screen: Display 2077752377 1440x900
Maximum Screen Size: 1440x900
VM arguments: [-Djava.library.path=/Applications/JOSM.app/Contents/MacOS, -DLibraryDirectory=${HOME}/Library, -DDocumentsDirectory=${HOME}/Documents, -DApplicationSupportDirectory=${HOME}/Library/Application Support, -DCachesDirectory=${HOME}/Library/Caches, -DApplicationDirectory=${HOME}/Applications, -DAutosavedInformationDirectory=${HOME}/Library/Autosave Information, -DDesktopDirectory=${HOME}/Desktop, -DDownloadsDirectory=${HOME}/Downloads, -DMoviesDirectory=${HOME}/Movies, -DMusicDirectory=${HOME}/Music, -DPicturesDirectory=${HOME}/Pictures, -DSharedPublicDirectory=${HOME}/Public, -DSystemLibraryDirectory=/Library, -DSystemApplicationSupportDirectory=/Library/Application Support, -DSystemCachesDirectory=/Library/Caches, -DSystemApplicationDirectory=/Applications, -DSystemUserDirectory=/Users, -DUserHome=${HOME}, -DSandboxEnabled=true, -DLaunchModifierFlags=0, -DLaunchModifierFlagCapsLock=false, -DLaunchModifierFlagShift=false, -DLaunchModifierFlagControl=false, -DLaunchModifierFlagOption=false, -DLaunchModifierFlagCommand=false, -DLaunchModifierFlagNumericPad=false, -DLaunchModifierFlagHelp=false, -DLaunchModifierFlagFunction=false, -Dapple.laf.useScreenMenuBar=true, -Dcom.apple.macos.use-file-dialog-packages=true, -Dcom.apple.macos.useScreenMenuBar=true, -Dcom.apple.mrj.application.apple.menu.about.name=JOSM, -Dcom.apple.smallTabs=true]
Dataset consistency test: No problems found

Last errors/warnings:
- W: No default layer selected, choosing first layer.
- E: Handled by bug report queue: java.lang.NullPointerException


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

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: AWT-EventQueue-0 (20) of main
java.lang.NullPointerException
	at org.openstreetmap.josm.data.imagery.WMTSTileSource$Layer.access$300(WMTSTileSource.java:211)
	at org.openstreetmap.josm.data.imagery.WMTSTileSource$SelectLayerDialog.getSelectedLayer(WMTSTileSource.java:332)
	at org.openstreetmap.josm.data.imagery.WMTSTileSource.userSelectLayer(WMTSTileSource.java:432)
	at org.openstreetmap.josm.actions.AddImageryLayerAction.convertImagery(AddImageryLayerAction.java:124)
	at org.openstreetmap.josm.actions.AddImageryLayerAction.actionPerformed(AddImageryLayerAction.java:162)
	at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967)
	at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308)
	at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
	at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
	at java.desktop/javax.swing.AbstractButton.doClick(AbstractButton.java:369)
	at java.desktop/com.apple.laf.ScreenMenuItem.actionPerformed(ScreenMenuItem.java:129)
	at java.desktop/java.awt.MenuItem.processActionEvent(MenuItem.java:690)
	at java.desktop/java.awt.MenuItem.processEvent(MenuItem.java:649)
	at java.desktop/java.awt.MenuComponent.dispatchEventImpl(MenuComponent.java:375)
	at java.desktop/java.awt.MenuComponent.dispatchEvent(MenuComponent.java:363)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:775)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
	at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
	at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
	at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

[Don-vip]

You have to select a layer. The button should be disabled, or a default entry selected.

[Don-vip]

In 16106/josm:

fix #18901 - NPE when no WMTS layer is selected