Action "Update multipolygon" may change route relation to multipolygon

[GerdP]

What steps will reproduce the problem?

1. load attached file
2. Select way with id 189944949 (amenity=parking)
3. Look at entry Tools -> Update multipolygon (Ctrl+Shift+B)

What is the expected result?

The entry for the action should be disabled

What happens instead?

The entry is enabled and clicking it will download missing members of the route relation and finally change the route relation to an invalid multipolygon.

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: 2019-04-28 04:36:41 +0200 (Sun, 28 Apr 2019)
Build-Date:2019-04-28 02:37:58
Revision:15031
Relative:URL: ^/trunk

Identification: JOSM/1.5 (15031 en) Windows 10 64-Bit
OS Build number: Windows 10 Home 1803 (17134)
Memory Usage: 704 MB / 1820 MB (262 MB allocated, but free)
Java version: 1.8.0_201-b09, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
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_20190529_074852.jfr]
Dataset consistency test: No problems found

Plugins:
+ OpeningHoursEditor (34977)
+ apache-commons (34908)
+ buildings_tools (34982)
+ continuosDownload (82)
+ ejml (34908)
+ geotools (34908)
+ jaxb (35014)
+ jts (34908)
+ o5m (34908)
+ opendata (34997)
+ pbf (34908)
+ poly (34991)
+ reverter (34999)
+ undelete (34977)
+ utilsplugin2 (34977)

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

Last errors/warnings:
- W: No configuration settings found.  Using hardcoded default values for all pools.