JabRef 5.0-beta.342--2020-01-15--58709e7
Linux 4.9.0-11-amd64 amd64
Java 13.0.2

When JabRef finds automatically the pdf of a reference in the file directory, the icon is not shown in the main table, and the link does not appear in the BibTeX source.

Steps to reproduce the behavior:

1. Create a new file
2. In the main file directory (defined in Options -> Preferences -> File -> External file links), put a file named test20.pdf
3. Create a new article entry
4. set the bibtexkey as "test20"
5. go to the "General tab"
   The linked file appears in the file field:
   
   In the BibTeX source tab, the file field is absent:
   
   In the main table, the file link icon is absent:
   

Note: log file is empty