Fix action helper

CHANGELOG.md

@@ -26,6 +26,7 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 - 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 with inconsistent capitalization of file extensions when downloading files [#6115](https://github.com/JabRef/jabref/issues/6115)
 - We fixed the display of language and encoding in the preferences dialog. [#6130](https://github.com/JabRef/jabref/pull/6130)
+- We fixed an error that sometimes occurred when using the context menu. [#6085](https://github.com/JabRef/jabref/issues/6085)
 - We fixed an issue where search full-text documents downloaded files with same name, overwriting existing files. [#6174](https://github.com/JabRef/jabref/pull/6174)
 
 ### Removed

src/main/java/org/jabref/gui/actions/ActionHelper.java

@@ -5,11 +5,15 @@
 
 import javafx.beans.binding.Bindings;
 import javafx.beans.binding.BooleanExpression;
+import javafx.collections.ObservableList;
 
 import org.jabref.gui.StateManager;
 import org.jabref.model.entry.BibEntry;
 import org.jabref.model.entry.field.Field;
 
+import org.fxmisc.easybind.EasyBind;
+import org.fxmisc.easybind.monadic.MonadicBinding;
+
 public class ActionHelper {
     public static BooleanExpression needsDatabase(StateManager stateManager) {
         return stateManager.activeDatabaseProperty().isPresent();
@@ -30,10 +34,12 @@ public static BooleanExpression isFieldSetForSelectedEntry(Field field, StateMan
     }
 
     public static BooleanExpression isAnyFieldSetForSelectedEntry(List<Field> fields, StateManager stateManager) {
-        BibEntry entry = stateManager.getSelectedEntries().get(0);
-        return Bindings.createBooleanBinding(
-                () -> entry.getFields().stream().anyMatch(fields::contains),
-                entry.getFieldsObservable(),
-                stateManager.getSelectedEntries());
+        ObservableList<BibEntry> selectedEntries = stateManager.getSelectedEntries();
+        MonadicBinding<Boolean> fieldsAreSet = EasyBind.monadic(Bindings.valueAt(selectedEntries, 0))
+                                                       .flatMap(entry -> Bindings.createBooleanBinding(() -> {
+                                                           return entry.getFields().stream().anyMatch(fields::contains);
+                                                       }, entry.getFieldsObservable()))
+                                                       .orElse(false);
+        return BooleanExpression.booleanExpression(fieldsAreSet);
     }
 }

src/main/java/org/jabref/gui/maintable/OpenFolderAction.java

@@ -27,17 +27,22 @@ public OpenFolderAction(DialogService dialogService, StateManager stateManager,
     @Override
     public void execute() {
         stateManager.getActiveDatabase().ifPresent(databaseContext ->
-            stateManager.getSelectedEntries().forEach(entry -> {
-                LinkedFileViewModel linkedFileViewModel = new LinkedFileViewModel(
-                        entry.getFiles().get(0),
-                        entry,
-                        databaseContext,
-                        Globals.TASK_EXECUTOR,
-                        dialogService,
-                        preferencesService.getXMPPreferences(),
-                        preferencesService.getFilePreferences(),
-                        ExternalFileTypes.getInstance());
-                linkedFileViewModel.openFolder();
-            }));
+                stateManager.getSelectedEntries().forEach(entry -> {
+                    if (entry.getFiles().isEmpty()) {
+                        return;
+                    }
+
+                    LinkedFileViewModel linkedFileViewModel = new LinkedFileViewModel(
+                            entry.getFiles().get(0),
+                            entry,
+                            databaseContext,
+                            Globals.TASK_EXECUTOR,
+                            dialogService,
+                            preferencesService.getXMPPreferences(),
+                            preferencesService.getFilePreferences(),
+                            ExternalFileTypes.getInstance()
+                    );
+                    linkedFileViewModel.openFolder();
+                }));
     }
 }