Fix exception when adding save action without selected formatter (#6072)

CHANGELOG.md

@@ -48,6 +48,7 @@ We refer to [GitHub issues](https://github.com/JabRef/jabref/issues) by using `#
 - We fixed an issue where the group and the link column were not updated after changing the entry in the main table. [#5985](https://github.com/JabRef/jabref/issues/5985)
 - We fixed an issue where reordering the groups was not possible after inserting an article. [#6008](https://github.com/JabRef/jabref/issues/6008)
 - We fixed an issue where citation styles except the default "Preview" could not be used. [#56220](https://github.com/JabRef/jabref/issues/5622)
+- We fixed an issue where an exception was thrown when adding a save action without a selected formatter in the library properties [#6069](https://github.com/JabRef/jabref/issues/6069)
 
 ### Removed
 

src/main/java/org/jabref/gui/cleanup/FieldFormatterCleanupsPanel.java

@@ -106,6 +106,7 @@ private void buildLayout() {
         actionsList = new ListView<>(actions);
         actionsList.setMinHeight(100.0);
         actionsList.getSelectionModel().setSelectionMode(SelectionMode.SINGLE);
+
         new ViewModelListCellFactory<FieldFormatterCleanup>()
                 .withText(action -> action.getField().getDisplayName() + ": " + action.getFormatter().getName())
                 .withStringTooltip(action -> action.getFormatter().getDescription())
@@ -179,6 +180,7 @@ private GridPane getSelectorPanel() {
                 .withStringTooltip(Formatter::getDescription)
                 .install(formattersCombobox);
         EasyBind.subscribe(formattersCombobox.valueProperty(), e -> updateDescription());
+        formattersCombobox.getSelectionModel().selectFirst();
         builder.add(formattersCombobox, 3, 1);
 
         addButton = new Button(Localization.lang("Add"));