Downloads from arxiv saved with wrong file suffix

[stefanct]

This is with the current snapshot (JabRef 5.0-dev--snapshot--2018-12-19--master--949d20496). Opening the attached bibtex library and trying to download the respective PDF via the entry's general tab leads to a file name ending in .01203v1 instead of .pdf. The contents are fine though. This is most probably due to the URL used by arxiv: https://arxiv.org/abs/1801.01203 but that shouldn't be an excuse ;)

arxiv.bib.txt

[Siedlerchr]

Thanks to @stefan-kolb this should be fixed in the latest master.

We would like to ask you to use a development build from https://builds.jabref.org/master and report back if it works for you. Please remember to make a backup of your library before trying-out this version.