Uncaught exception on startup with a database

[wujastyk]

JabRef version

JabRef 5.0.0-dev--2019-10-17----26a1d29a3
Linux 5.0.0-31-generic amd64
Java 12.0.2

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

Steps to reproduce the behavior:

1. Start the program with a couple of databases open from the last session. The exception box pops up immediately.

The problem might be connected with having custom entry types in the database:

1. close all databases
2. open database with three custom entry types:

@Comment{jabref-meta: saveOrderConfig:specified;author;false;date;false;title;true;}

@Comment{jabref-entrytype: manuscript: req[collection;library;location;shelfmark;shortcollection;shorthand;shortlibrary] opt[pagetotal;pagination;origin;catalog;columns;bookpagination;keywords;scribe;layer;annotation;contents;owner;dating;support;pages]}

@Comment{jabref-entrytype: review: req[author;date;journal;number;pages;related;relatedtype;volume] opt[url;urldate;doi]}

@Comment{jabref-entrytype: audio: req[author;date;editor;editortype;number;publisher;series;title;type] opt[url;urldate]}

And then I get a blank popup:

Log File

java.lang.IllegalStateException: Not on FX application thread; currentThread = JabRef CachedThreadPool
  at org.jabref.merged.module/com.sun.javafx.tk.Toolkit.checkFxUserThread(Unknown Source)
  at org.jabref.merged.module/com.sun.javafx.tk.quantum.QuantumToolkit.checkFxUserThread(Unknown Source)
  at org.jabref.merged.module/javafx.stage.Stage.<init>(Unknown Source)
  at org.jabref.merged.module/javafx.stage.Stage.<init>(Unknown Source)
  at org.jabref.merged.module/javafx.scene.control.HeavyweightDialog$1.<init>(Unknown Source)
  at org.jabref.merged.module/javafx.scene.control.HeavyweightDialog.<init>(Unknown Source)
  at org.jabref.merged.module/javafx.scene.control.Dialog.<init>(Unknown Source)
  at org.jabref/org.jabref.gui.util.BaseDialog.<init>(Unknown Source)
  at org.jabref/org.jabref.gui.importer.ImportCustomEntryTypesDialog.<init>(Unknown Source)
  at org.jabref/org.jabref.gui.importer.actions.CheckForNewEntryTypesAction.performAction(Unknown Source)
  at org.jabref/org.jabref.gui.importer.actions.OpenDatabaseAction.performPostOpenActions(Unknown Source)
  at org.jabref/org.jabref.JabRefGUI.openDatabases(Unknown Source)
  at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
  at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
  at java.base/java.lang.Thread.run(Unknown Source)

[matthiasgeiger]

Thank you for reporting this issue. We think, that is already fixed in our development version and consequently the change will be included in the next release.

We would like to ask you to use a development build from https://builds.jabref.org/master.