fix: address issues with concurrency in DefaultFileUpdateMonitor (Jab…

…Ref#10585)

Changed the MultiMap into a synchronized type for safety

Used the Platform.runLater() to ensure processes are executed on correct threads

Not sure what the side effects of these fixes are

src/main/java/org/jabref/gui/util/DefaultFileUpdateMonitor.java

@@ -12,13 +12,16 @@
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 
+import javafx.application.Platform;
+
 import org.jabref.logic.JabRefException;
 import org.jabref.logic.WatchServiceUnavailableException;
 import org.jabref.model.util.FileUpdateListener;
 import org.jabref.model.util.FileUpdateMonitor;
 
 import com.google.common.collect.ArrayListMultimap;
 import com.google.common.collect.Multimap;
+import com.google.common.collect.Multimaps;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -32,7 +35,7 @@ public class DefaultFileUpdateMonitor implements Runnable, FileUpdateMonitor {
 
     private static final Logger LOGGER = LoggerFactory.getLogger(DefaultFileUpdateMonitor.class);
 
-    private final Multimap<Path, FileUpdateListener> listeners = ArrayListMultimap.create(20, 4);
+    private final Multimap<Path, FileUpdateListener> listeners = Multimaps.synchronizedListMultimap(ArrayListMultimap.create(20, 4));
     private volatile WatchService watcher;
     private final AtomicBoolean notShutdown = new AtomicBoolean(true);
     private final AtomicReference<Optional<JabRefException>> filesystemMonitorFailure = new AtomicReference<>(Optional.empty());
@@ -82,7 +85,7 @@ public boolean isActive() {
     }
 
     private void notifyAboutChange(Path path) {
-        listeners.get(path).forEach(FileUpdateListener::fileUpdated);
+        Platform.runLater(() -> listeners.get(path).forEach(FileUpdateListener::fileUpdated));
     }
 
     @Override