JabRef version 5.x on Ubuntu 18.04 LTS

• [ x] I have tested the latest development version from http://builds.jabref.org/master/ and the problem persists

Steps to reproduce the behavior:

1. Manual connect to Libreoffice (Auto connect generates same error)
2. Specify directory for .jar class files: /usr/lib/libreoffice/program/classes (have double-checked that they are actually there)
3. Click OK
4. Error: "Could not connect to running OpenOffice/LibreOffice
   (Not all) required OpenOffice jars were found inside the installation path. Searched for [unoil.jar, jurt.jar, juh.jar., ridl.jar] in /opt/openoffice.org3"

Stacktrace:

java.io.IOException: (Not all) required Open Office Jars were found inside installation path. Searched for [unoil.jar, jurt.jar, juh.jar, ridl.jar] in /opt/openoffice.org3
at org.jabref.gui.openoffice.OpenOfficePanel.loadOpenOfficeJars(OpenOfficePanel.java:449)
at org.jabref.gui.openoffice.OpenOfficePanel$2.call(OpenOfficePanel.java:389)
at org.jabref.gui.openoffice.OpenOfficePanel$2.call(OpenOfficePanel.java:384)
at javafx.concurrent.Task$TaskCallable.call(Task.java:1425)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:834)