JabRef versions 3.3 - 3.7 on Ubuntu 14.04 and 16.04.

Steps to reproduce:

1. Download JabRef's jar file for any of the releases 3.3 to 3.7
2. Create or find a bib file, references.bib, say (an example is given below)
3. Try java -jar JabRef-3.7.jar -n -o references.html,tablerefsabsbib references.bib (other export formats do not work either)

In current JabRef 3.7, no html file is produced and the output is:

09:57:04.556 [AWT-EventQueue-0] INFO  net.sf.jabref.logic.importer.OpenDatabase - Opening: references.bib
Exporting: references.html
Could not export file 'references.html': null

Note: exporting bibfiles via the GUI works flawlessly.

In JabRef 3.2, the html file is produced correctly and the output is:

Nov 15, 2016 9:51:39 AM net.sf.jabref.JabRef openBibFile
INFO: Opening: references.bib
Exporting: references.html
Nov 15, 2016 9:51:39 AM net.sf.jabref.exporter.ExportFormat performExport
WARNING: []

I used the following simple references.bib:

@Book{key,
  Title = {Title},
  Author = {An Author},
  Publisher = {A Publisher},
  Year = {2016},
  Address = {Address}
}