JabRef 5.1--2020-04-21--dc1e339 Linux 5.3.0-46-generic amd64 Java 14.0.1 <!-- IMPORTANT NOTE -> <!-- Please always test if the bug is still reproducible in the latest development version. We are constantly improving JabRef and some bugs may already be fixed. You can download the development version at: http://builds.jabref.org/master/ Please make a backup of your library before you try out this version. If you already use a development version, ensure that you use the latest one. --> - [ x] I have tested the latest development version from http://builds.jabref.org/master/ and the problem persists <!-- Add a clear and concise description of what the bug is. --> Steps to reproduce the behavior: 1. Options/Preferences/Entry Preview 2. add some journal styles 3. hit "save". Error popup, as shown below <!-- If applicable, add excerpt of the bibliography file, screenshot, and excerpt of log (available in the error console) -->  and  <details> <summary>Log File</summary> ``` Paste an excerpt of your log file here ``` </details>
JabRef 5.1--2020-04-21--dc1e339
Linux 5.3.0-46-generic amd64
Java 14.0.1
Steps to reproduce the behavior:
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Log File