Fix Autosave threading issue

CHANGELOG.md

@@ -38,6 +38,7 @@ We refer to [GitHub issues](https://github.com/JabRef/jabref/issues) by using `#
 - We fixed an issue where an entry containing an external filename with curly braces could not be saved. Curly braces are now longer allowed in filenames. [#5899](https://github.com/JabRef/jabref/issues/5899)
 - We fixed an issue where changing the type of an entry did not update the main table. [#5906](https://github.com/JabRef/jabref/issues/5906)
 - We fixed an issue where opening a library from the recent libraries menu was not possible. [#5939](https://github.com/JabRef/jabref/issues/5939)
+- We fixed an issue where Autosave actions could lead to an exception. [#5658](https://github.com/JabRef/jabref/issues/5658)
 
 ### Removed
 

src/main/java/org/jabref/gui/dialogs/AutosaveUIManager.java

@@ -3,6 +3,7 @@
 import org.jabref.Globals;
 import org.jabref.gui.BasePanel;
 import org.jabref.gui.exporter.SaveDatabaseAction;
+import org.jabref.gui.util.DefaultTaskExecutor;
 import org.jabref.model.database.event.AutosaveEvent;
 
 import com.google.common.eventbus.Subscribe;
@@ -26,7 +27,9 @@ public AutosaveUIManager(BasePanel panel) {
     @Subscribe
     public void listen(@SuppressWarnings("unused") AutosaveEvent event) {
         try {
-            new SaveDatabaseAction(panel, Globals.prefs, Globals.entryTypesManager).save(SaveDatabaseAction.SaveDatabaseMode.SILENT);
+            DefaultTaskExecutor.runAndWaitInJavaFXThread(() -> {
+                new SaveDatabaseAction(panel, Globals.prefs, Globals.entryTypesManager).save(SaveDatabaseAction.SaveDatabaseMode.SILENT);
+            });
         } catch (Throwable e) {
             LOGGER.error("Problem occurred while saving.", e);
         }

src/main/java/org/jabref/gui/exporter/SaveDatabaseAction.java

@@ -45,6 +45,8 @@
  * <p>
  * The save operation is loaded off of the GUI thread using {@link BackgroundTask}. Callers can query whether the
  * operation was canceled, or whether it was successful.
+ * However, the callee must make sure that methods are called from the JavaFX application thread as {@link BasePanel}
+ * and {@link JabRefFrame} are manipulated during saving operations.
  */
 public class SaveDatabaseAction {