DataIntegrityProblemException: Primitive must be part of the dataset - MendRelationAction

[Polyglot]

What steps will reproduce the problem?

1. pressed 9 twice
2. then 1, but it looked odd, as if a fork still needed splitting, I'll send link to video I'm recording later on

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: 2018-08-12 02:52:44 +0200 (Sun, 12 Aug 2018)
Build-Date:2018-08-12 01:33:39
Revision:14139
Relative:URL: ^/trunk

Identification: JOSM/1.5 (14139 en) Linux Mint 18.3 Sylvia
Memory Usage: 2153 MB / 2711 MB (264 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:
+ ImportImagePlugin
+ Mapillary (v1.5.15)
+ OpeningHoursEditor (34389)
+ apache-commons (34389)
+ apache-http (34389)
+ buildings_tools (34212)
+ ejml (34389)
+ geotools (34125)
+ jts (34206)
+ log4j
+ 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:
- W: java.io.IOException: Attribution is not loaded yet
- W: java.io.IOException: Attribution is not loaded yet
- W: java.io.IOException: Attribution is not loaded yet
- W: java.io.IOException: Attribution is not loaded yet
- W: Invalid jar file ''<josm.userdata>/plugins/log4j.jar.new'' (exists: false, canRead: false)
- W: Invalid jar file ''<josm.userdata>/plugins/ImportImagePlugin.jar.new'' (exists: false, canRead: false)
- W: Could not read from URL https://a.mapillary.com/v3/detections?client_id=T1Fzd20xZjdtR0s1VDk5OFNIOXpYdzoxNDYyOGRkYzUyYTFiMzgz&bbox=4.6619582%2C50.8770036%2C4.6653914%2C50.8786554!: java.io.IOException: Server returned HTTP response code: 504 for URL: https://a.mapillary.com/v3/detections?client_id=T1Fzd20xZjdtR0s1VDk5OFNIOXpYdzoxNDYyOGRkYzUyYTFiMzgz&bbox=4.6619582%2C50.8770036%2C4.6653914%2C50.8786554
- W: Could not read from URL https://a.mapillary.com/v3/detections?client_id=T1Fzd20xZjdtR0s1VDk5OFNIOXpYdzoxNDYyOGRkYzUyYTFiMzgz&bbox=4.6899605%2C50.8682969%2C4.6988869%2C50.871926!: java.io.IOException: Server returned HTTP response code: 504 for URL: https://a.mapillary.com/v3/detections?client_id=T1Fzd20xZjdtR0s1VDk5OFNIOXpYdzoxNDYyOGRkYzUyYTFiMzgz&bbox=4.6899605%2C50.8682969%2C4.6988869%2C50.871926
- E: Handled by bug report queue: java.lang.IllegalArgumentException: Parameter 'data' must not be null
- E: Handled by bug report queue: org.openstreetmap.josm.data.osm.DataIntegrityProblemException: Primitive must be part of the dataset: {Way id=-26804810 version=0 VT nodes=[{Node id=302030926 version=7 V lat=49.2423937,lon=4.0406764}, {Node id=352811200 version=4 V lat=49.2420106,lon=4.0409428}]}


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

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: AWT-EventQueue-0 (18) of main
org.openstreetmap.josm.data.osm.DataIntegrityProblemException: Primitive must be part of the dataset: {Way id=-26804810 version=0 VT nodes=[{Node id=302030926 version=7 V lat=49.2423937,lon=4.0406764}, {Node id=352811200 version=4 V lat=49.2420106,lon=4.0409428}]}
	at org.openstreetmap.josm.data.osm.OsmPrimitive.checkDataset(OsmPrimitive.java:247)
	at org.openstreetmap.josm.data.osm.OsmPrimitive.getReferrers(OsmPrimitive.java:826)
	at org.openstreetmap.josm.data.osm.OsmPrimitive.getReferrers(OsmPrimitive.java:848)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction.isRestricted(MendRelationAction.java:1281)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction.removeInvalidWaysFromParentWays(MendRelationAction.java:1066)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction.goToNextWays(MendRelationAction.java:818)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction.findNextWayAfterDownload(MendRelationAction.java:653)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction.downloadAreaAroundWay(MendRelationAction.java:1159)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction.findNextWayBeforeDownload(MendRelationAction.java:621)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction.callNextWay(MendRelationAction.java:321)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction.downloadAreaAroundWay(MendRelationAction.java:1200)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction.callNextWay(MendRelationAction.java:331)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction.getNextWayAfterSelection(MendRelationAction.java:1974)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction$2.keyPressed(MendRelationAction.java:1659)
	at java.awt.Component.processKeyEvent(Component.java:6491)
	at javax.swing.JComponent.processKeyEvent(JComponent.java:2832)
	at java.awt.Component.processEvent(Component.java:6310)
	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.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1954)
	at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:835)
	at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:1103)
	at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:974)
	at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:800)
	at java.awt.Component.dispatchEventImpl(Component.java:4760)
	at java.awt.Container.dispatchEventImpl(Container.java:2296)
	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)

[Polyglot]

​https://www.youtube.com/watch?v=Qjl1jjexeoA

[Don-vip]

Closed as duplicate of #16583.