Error: Uncaught exception occured in Thread [JavaFX Application Thread,5,main]

[rezaeimohammad]

I tested it for two versions:

JabRef 5.0--2020-03-06--2e6f433
Linux 5.6.0-1-amd64 amd64
Java 13.0.2. -->
and
JabRef 5.1--2020-05-29--ed275b6
Linux 5.6.0-1-amd64 amd64
Java 14.0.1

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

Steps to reproduce the behavior:
when I turn on linux, the Jabref work perfectly but when I close it and I tried to rerun it the follow error appear:

java.lang.NullPointerException: You need to start the file monitor before watching files at java.base/java.util.Objects.requireNonNull(Unknown Source) at org.jabref/org.jabref.gui.util.DefaultFileUpdateMonitor.addListenerForFile(Unknown Source) at org.jabref/org.jabref.gui.collab.DatabaseChangeMonitor.lambda$new$0(Unknown Source) at java.base/java.util.Optional.ifPresent(Unknown Source) at org.jabref/org.jabref.gui.collab.DatabaseChangeMonitor.<init>(Unknown Source) at org.jabref/org.jabref.gui.BasePanel.resetChangeMonitorAndChangePane(Unknown Source) at org.jabref/org.jabref.gui.BasePanel.setupMainPanel(Unknown Source) at org.jabref/org.jabref.gui.BasePanel.<init>(Unknown Source) at org.jabref/org.jabref.gui.importer.actions.OpenDatabaseAction.addNewDatabase(Unknown Source) at org.jabref/org.jabref.gui.importer.actions.OpenDatabaseAction.lambda$openTheFile$1(Unknown Source) at org.jabref/org.jabref.gui.util.DefaultTaskExecutor.lambda$getJavaFXTask$3(Unknown Source) at org.jabref.merged.module/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source) at org.jabref.merged.module/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source) at org.jabref.merged.module/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source) at org.jabref.merged.module/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source) at org.jabref.merged.module/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source) at org.jabref.merged.module/com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source) at org.jabref.merged.module/com.sun.javafx.event.EventUtil.fireEvent(Unknown Source) at org.jabref.merged.module/javafx.event.Event.fireEvent(Unknown Source) at org.jabref.merged.module/javafx.concurrent.EventHelper.fireEvent(Unknown Source) at org.jabref.merged.module/javafx.concurrent.Task.fireEvent(Unknown Source) at org.jabref.merged.module/javafx.concurrent.Task.setState(Unknown Source) at org.jabref.merged.module/javafx.concurrent.Task$TaskCallable.lambda$call$1(Unknown Source) at org.jabref.merged.module/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(Unknown Source) at java.base/java.security.AccessController.doPrivileged(Unknown Source) at org.jabref.merged.module/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(Unknown Source) at org.jabref.merged.module/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source) at org.jabref.merged.module/com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method) at org.jabref.merged.module/com.sun.glass.ui.gtk.GtkApplication.lambda$runLoop$11(Unknown Source) at java.base/java.lang.Thread.run(Unknown Source)

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[github-actions]

This issue has been inactive for half a year. Since JabRef is constantly evolving this issue may not be relevant any longer and it will be closed in two weeks if no further activity occurs.

As part of an effort to ensure that the JabRef team is focusing on important and valid issues, we would like to ask if you could update the issue if it still persists. This could be in the following form:

• If there has been a longer discussion, add a short summary of the most important points as a new comment (if not yet existing).
• Provide further steps or information on how to reproduce this issue.
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