Automatic Bug Report - 20190105211612

JabRef 5.0-dev--snapshot--2019-01-05--master--e1cfec9c5
Windows 10 10.0 amd64 
Java 1.8.0_191

Steps to reproduce:

1. ...
2. ...
3. ...

<details>
<summary>Detail information:</summary>

```
Uncaught exception occurred in Thread[JavaFX Application Thread,5,main]
```

</details>
