Warn when openin invalid geojson

[Stereo]

What steps will reproduce the problem?

1. Open JOSM
2. Open ​https://github.com/osmlab/editor-layer-index/blob/gh-pages/sources/north-america/us/USGSImagery.geojson - note that this isn't a valid geojson

What is the expected result?

An error message saying "This isn't a valid geojson (you fool)"

What happens instead?

Exception

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: 2019-12-01 23:10:15 +0100 (Sun, 01 Dec 2019)
Build-Date:2019-12-02 02:30:57
Revision:15553
Relative:URL: ^/trunk

Identification: JOSM/1.5 (15553 en_GB) Mac OS X 10.15.2
OS Build number: Mac OS X 10.15.2 (19C57)
Memory Usage: 860 MB / 1820 MB (298 MB allocated, but free)
Java version: 1.8.0_231-b11, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Screen: Display 2077748985 1792x1120
Maximum Screen Size: 1792x1120
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=1048576, -DLaunchModifierFlagCapsLock=false, -DLaunchModifierFlagShift=false, -DLaunchModifierFlagControl=false, -DLaunchModifierFlagOption=false, -DLaunchModifierFlagCommand=true, -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]

Plugins:
+ AddrInterpolation (35248)
+ CommandLine (35248)
+ ImportImagePlugin (35248)
+ Mapillary (1.5.20)
+ MovementAlert (1511141840)
+ OpeningHoursEditor (35250)
+ PicLayer (35248)
+ ShapeTools (1240)
+ alignways (35248)
+ apache-commons (35092)
+ apache-http (35092)
+ areaselector (359)
+ austriaaddresshelper (57)
+ buildings_tools (35248)
+ changeset-viewer (22)
+ conflation (0.6.4)
+ continuosDownload (82)
+ contourmerge (v0.1.5)
+ ejml (35122)
+ geotools (35169)
+ jaxb (35092)
+ jna (35092)
+ jogl (1.2.3)
+ jts (35122)
+ log4j (35092)
+ opendata (35248)
+ openqa (0.1.9)
+ public_transport (35248)
+ reltoolbox (35248)
+ reverter (35248)
+ rex (53)
+ splinex (35248)
+ terracer (35248)
+ todo (30306)
+ turnrestrictions (35248)
+ undelete (35248)
+ utilsplugin2 (35248)
+ wikipedia (1.1.3)

Tagging presets:
+ https://josm.openstreetmap.de/josmfile?page=Presets/NewTags&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/BicycleJunction&preset&zip=1
+ http://osmtools.de/josm/steps.xml
+ https://josm.openstreetmap.de/josmfile?page=Presets/Historic_Stone&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/LaneAttributes&preset&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/Towers&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/Golf_Course&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/PublicTransportOneClick&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/Bus_lanes&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/Heritage&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/Historical_Objects&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/public_bookcase&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/Stolpersteine&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/BuildingPreset&zip=1

Map paint styles:
- https://josm.openstreetmap.de/josmfile?page=Styles/Lit&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/ParkingLanes&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Surface&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Maxspeed&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Modified&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/LessObtrusiveNodes&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/AddressValidator&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Noname&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Power&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Surface-DataEntry&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/PowerMapping&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Lane_and_Road_Attributes&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/BesideTheRoad_Speed&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/TreeCrownDiameter&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/SlovakiaBicycleRoutes&style&zip=1
- https://github.com/simon04/coloured-addresses.mapcss/raw/master/dist/coloured-addresses.mapcss
- https://josm.openstreetmap.de/josmfile?page=Styles/Coloured_Streets&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Coloured_Suburb&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Cycleways&style&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/SlovakiaBicycleRoutes&style&zip=1
- https://github.com/GlassOceanos/indoor-JOSM-style/archive/master.zip
- https://josm.openstreetmap.de/josmfile?page=Styles/PublicTransport&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/PTStops&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/SlovakiaBicycleRoutes&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/SimpleRoofTags&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/SimpleBuildingTags&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/HiDPISupport&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/NumberedCycleNodeNetworks&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/NumberedWalkingNodeNetworks&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/AddressValidator&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/NewHighwayColors&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Noname&zip=1

Validator rules:
+ http://www.openrailwaymap.org/validator/openrailwaymap.validator.mapcss
+ https://josm.openstreetmap.de/josmfile?page=Rules/GermanySpecific&zip=1
+ http://www.openrailwaymap.org/validator/de-openrailwaymap.validator.mapcss
+ https://josm.openstreetmap.de/josmfile?page=Rules/MissingWeekdays&zip=1
+ https://raw.githubusercontent.com/nlehuby/transport_mapcss/master/transport.validator.mapcss

Last errors/warnings:
- W: java.net.ConnectException: Connection refused (Connection refused)
- W: java.net.ConnectException: Connection refused (Connection refused)
- W: java.net.ConnectException: Connection refused (Connection refused)
- W: Already here java.net.ConnectException: Connection refused (Connection refused)
- W: Failed to load Mappaint styles from 'http://maps.openstreetmap.ie/josm/townland.mapcss'. Exception was: java.net.ConnectException: Connection refused (Connection refused)
- E: java.net.ConnectException: Connection refused (Connection refused)
- W: No configuration settings found.  Using hardcoded default values for all pools.
- W: Region [TMS_BLOCK_v2] Resetting cache
- W: Warning: Failed to scan file 'fr.datagouvfr.jar' for module information. Skipping.
- E: Handled by bug report queue: javax.json.stream.JsonParsingException: Unexpected char 60 at (line no=7, column no=1, offset=6)


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

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: main-worker-0 (80) of main
javax.json.stream.JsonParsingException: Unexpected char 60 at (line no=7, column no=1, offset=6)
	at org.glassfish.json.JsonTokenizer.unexpectedChar(JsonTokenizer.java:601)
	at org.glassfish.json.JsonTokenizer.nextToken(JsonTokenizer.java:418)
	at org.glassfish.json.JsonParserImpl$NoneContext.getNextEvent(JsonParserImpl.java:413)
	at org.glassfish.json.JsonParserImpl.next(JsonParserImpl.java:363)
	at org.openstreetmap.josm.io.GeoJSONReader.parse(GeoJSONReader.java:65)
	at org.openstreetmap.josm.io.GeoJSONReader.doParseDataSet(GeoJSONReader.java:349)
	at org.openstreetmap.josm.io.GeoJSONReader.parseDataSet(GeoJSONReader.java:363)
	at org.openstreetmap.josm.gui.io.importexport.GeoJSONImporter.importData(GeoJSONImporter.java:51)
	at org.openstreetmap.josm.gui.io.importexport.FileImporter.importDataHandleExceptions(FileImporter.java:95)
	at org.openstreetmap.josm.actions.OpenFileAction$OpenFileTask.importData(OpenFileAction.java:367)
	at org.openstreetmap.josm.actions.OpenFileAction$OpenFileTask.realRun(OpenFileAction.java:319)
	at org.openstreetmap.josm.gui.PleaseWaitRunnable.doRealRun(PleaseWaitRunnable.java:94)
	at org.openstreetmap.josm.gui.PleaseWaitRunnable.run(PleaseWaitRunnable.java:142)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

[Don-vip]

In 15620/josm:

fix #18466 - catch JsonParsingException when loading geojson files