Using directupload plugin fails, then I get an 'unexpected error'

[Beddhist]

What steps will reproduce the problem?

1. During editing, load a GPS track
2. After uploading changes, hilight the track and press Ctrl-G to upload it.
3. Fill in tags and description. Click Upload

What is the expected result?

GPS track is uploaded.

What happens instead?

Dialog Box is displayed titled 'Update plugins': "An unexpected exception occurred that may have come from the plugin DirectUpload." There are 4 buttons, "Update", "Disable", "Keep" and "Help". Update closes the box and a few secs later there is another "Unexpected exception".

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

JOSM is started from the web and manual plugin update says they are all up-to-date.

URL:http://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2016-03-13 01:17:21 +0100 (Sun, 13 Mar 2016)
Build-Date:2016-03-13 02:35:00
Revision:9979
Relative:URL: ^/trunk

Identification: JOSM/1.5 (9979 en) Windows 7 64-Bit
Memory Usage: 247 MB / 247 MB (44 MB allocated, but free)
Java version: 1.8.0_74-b02, Oracle Corporation, Java HotSpot(TM) Client VM
VM arguments: [-Djava.security.manager, -Djava.security.policy=file:C:\Program Files (x86)\Java\jre1.8.0_74\lib\security\javaws.policy, -DtrustProxy=true, -Djnlpx.home=<java.home>\bin, -Djnlpx.origFilenameArg=C:\Users\Peter\AppData\Local\Temp\josm.jnlp, -Djnlpx.remove=true, -Djava.util.Arrays.useLegacyMergeSort=true, -Djnlpx.splashport=57642, -Djnlpx.jvm=<java.home>\bin\javaw.exe, -Djnlpx.vmargs=LURqYXZhLnV0aWwuQXJyYXlzLnVzZUxlZ2FjeU1lcmdlU29ydD10cnVlAA==]
Dataset consistency test: No problems found

Plugins:
- DirectUpload (31912)
- imagery_offset_db (32046)
- turnrestrictions (31895)
- utilsplugin2 (32099)

Last errors/warnings:
- E: Failed to locate image 'Flag, Blue'
- E: Failed to locate image 'Flag, Blue'
- E: Failed to locate image 'Flag, Blue'
- E: java.lang.NoSuchMethodError: org.openstreetmap.josm.tools.HttpClient.setFixedLengthStreamingMode(J)Lorg/openstreetmap/josm/tools/HttpClient;
- E: java.lang.NoSuchMethodError: org.openstreetmap.josm.tools.HttpClient.setFixedLengthStreamingMode(J)Lorg/openstreetmap/josm/tools/HttpClient;

java.lang.NoSuchMethodError: org.openstreetmap.josm.tools.HttpClient.setFixedLengthStreamingMode(J)Lorg/openstreetmap/josm/tools/HttpClient;
	at org.openstreetmap.josm.plugins.DirectUpload.UploadDataGui.setupConnection(UploadDataGui.java:285)
	at org.openstreetmap.josm.plugins.DirectUpload.UploadDataGui.upload(UploadDataGui.java:232)
	at org.openstreetmap.josm.plugins.DirectUpload.UploadDataGui.access$700(UploadDataGui.java:50)
	at org.openstreetmap.josm.plugins.DirectUpload.UploadDataGui$6.realRun(UploadDataGui.java:431)
	at org.openstreetmap.josm.gui.PleaseWaitRunnable.doRealRun(PleaseWaitRunnable.java:93)
	at org.openstreetmap.josm.gui.PleaseWaitRunnable.run(PleaseWaitRunnable.java:161)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)

[Beddhist]

2 GPX tracks to upload

[Don-vip]

Closed as duplicate of #12686.