empty field should not be added

[hanachaari]

1. Reset JabRef preferences

2. Restart JabRef

3. start preferences -> entry table

4. 

5. press the drop-down list button without selecting anything then press add button

expected: dismiss the empty column . But a new column "Custom" is added.

[koppor]

@hanachaari Do you want to work on a fix - or are you "just" reporting?

[hanachaari]

Just reporting. I am working on issue #566 currently

[Siedlerchr]

Thanks for reporting those. Please do report JabRef issues at the JabRef repo. https://github.com/JabRef/jabref/issues
Koppor's repo is just for dev purposes.