plugins update with new (last) josm version fails with error

[anonymous]

how to reproduce:
1) download the last josm version to update an old one.
2) start it; an plugin update dialog will be shown on the 1st start - confirm it to update
(but does it really update all necessary plugins! see bottom and files)
3) open the preferences dialog and click on 5th. button for plugins.
4) for one second you can see a dialog (perhaps for reading the plugins information/version but it is to fast the read)
5) then you get the error message dialog

please see the 1st. error-message file;
some plugins have no version number info!

so i close the error-dialog and push the plugins-update button; and the download-window has updated some plugins again (i think the same plugins as on josm start up - but i am not quite sure)
after download is finished i closed josm and start it again;
call the preferences and the plugin picture-button again;
and the same error happens once again and i saved the (second-try) error message once more.

please look to the second error-message file;
i saved a picture of this 2nd. try of the downloaded plugins.
(for the first try i do not have a picture, sorry)

now you can see the differences between the two messages;
some plugins ARE updated between the first and the second start but other ARE NOT or have no version number!!!

there seems to be a problem to read the version of the following plugins:

openstreetbugs (20696 is downloaded, see picture)
editgpx (19683 is downloaded; see picture)
validator (21177 is downloaded, see picture)
turnrestrictions (21186 is downloaded, see picture)

some plugins ARE NOT updated on the first try but on the second:
osmarender (Version: 19419) --> (Version: 21268)!!!
measurement (Version: 19681) ---> (Version: 21307) !!!

but it was really the 3rd!! try/download because on new-josm-version start up, we are automatically asked to update the plugins because of the new version of josm and we confirmed it on the first start (see above)
i do not remember if i activate one plugin more (tagging-preset-tester???) but there is one more listed now on the second start (9 instead of 8); i thought - i did not, but now i am unsafe

[stoecker]

Closed as duplicate of #4984.