NPE at org.openstreetmap.josm.gui.dialogs.relation.ReferringRelationsBrowserModel.canReload()

[GerdP]

What steps will reproduce the problem?

1. Make sure that preference multipoly.show-relation-editor is set to true
2. draw new closed way
3. select existing way which is a member of a multipolygon relation
4. Update multipolygon (Ctrl+Shift+B)

What is the expected result?

Relation Editor is shown with the freshly updated multipolygon

What happens instead?

error popup

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

Found this while looking at #19346

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2020-06-02 08:27:29 +0200 (Tue, 02 Jun 2020)
Build-Date:2020-06-02 11:11:35
Revision:16538
Relative:URL: ^/trunk

Identification: JOSM/1.5 (16538 en) Windows 10 64-Bit
OS Build number: Windows 10 Home 1903 (18362)
Memory Usage: 937 MB / 3641 MB (552 MB allocated, but free)
Java version: 1.8.0_221-b11, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Look and Feel: com.sun.java.swing.plaf.windows.WindowsLookAndFeel
Screen: \Display0 1920x1080
Maximum Screen Size: 1920x1080
VM arguments: [-XX:StartFlightRecording=name=MyRecording2,settings=d:\dbg\gerd.jfc, -XX:FlightRecorderOptions=defaultrecording=true,dumponexit=true,dumponexitpath=e:\ld\perf_20200607_113718.jfr]
Dataset consistency test: No problems found

Plugins:
+ OpeningHoursEditor (35414)
+ apache-commons (35362)
+ buildings_tools (35474)
+ continuosDownload (91)
+ ejml (35313)
+ geotools (35169)
+ jaxb (35092)
+ jts (35122)
+ merge-overlap (35248)
+ o5m (35248)
+ opendata (35405)
+ pbf (35446)
+ poly (35248)
+ reverter (35474)
+ undelete (35474)
+ utilsplugin2 (35476)

Validator rules:
+ c:\josm\core\resources\data\validator\geometry.mapcss

Last errors/warnings:
- E: Handled by bug report queue: java.lang.NullPointerException
- 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 (21) of main
java.lang.NullPointerException
	at org.openstreetmap.josm.gui.dialogs.relation.ReferringRelationsBrowserModel.canReload(ReferringRelationsBrowserModel.java:107)
	at org.openstreetmap.josm.gui.dialogs.relation.ReferringRelationsBrowser$ReloadAction.refreshEnabled(ReferringRelationsBrowser.java:115)
	at org.openstreetmap.josm.gui.dialogs.relation.ReferringRelationsBrowser$ReloadAction.<init>(ReferringRelationsBrowser.java:111)
	at org.openstreetmap.josm.gui.dialogs.relation.ReferringRelationsBrowser.build(ReferringRelationsBrowser.java:80)
	at org.openstreetmap.josm.gui.dialogs.relation.ReferringRelationsBrowser.<init>(ReferringRelationsBrowser.java:53)
	at org.openstreetmap.josm.gui.dialogs.relation.GenericRelationEditor.<init>(GenericRelationEditor.java:237)
	at org.openstreetmap.josm.gui.dialogs.relation.RelationEditor.getEditor(RelationEditor.java:81)
	at org.openstreetmap.josm.actions.CreateMultipolygonAction$CreateUpdateMultipolygonTask.lambda$run$0(CreateMultipolygonAction.java:128)
	at java.awt.event.InvocationEvent.dispatch(Unknown Source)
	at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
	at java.awt.EventQueue.access$500(Unknown Source)
	at java.awt.EventQueue$3.run(Unknown Source)
	at java.awt.EventQueue$3.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.run(Unknown Source)

[GerdP]

In 16554/josm:

fix #19355: NPE at org.openstreetmap.josm.gui.dialogs.relation.ReferringRelationsBrowserModel.canReload()

• don't use relation created by createMultipolygonCommand as it was not yet added to the dataset
• get the correct relation after command was executed

(maybe RelationEditor.getEditor() is the better place to do this, adding a null check in canReload() makes no sense as other methods also cannot handle a relation without dataset)