Open theme browse in last css dir (#11597)

* Open theme browse in last css dir

* add changelog

CHANGELOG.md

@@ -32,6 +32,7 @@ Note that this project **does not** adhere to [Semantic Versioning](https://semv
 - JabRef does not show finished background tasks in the status bar popup. [#11574](https://github.com/JabRef/jabref/pull/11574)
 - We enhanced the indexing speed. [#11502](https://github.com/JabRef/jabref/pull/11502)
 - ⚠️ Renamed command line parameters `embeddBibfileInPdf` to `embedBibFileInPdf`, `writeMetadatatoPdf` to `writeMetadataToPdf`, and `writeXMPtoPdf` to `writeXmpToPdf`. [#11575](https://github.com/JabRef/jabref/pull/11575)
+- The browse button for a Custom theme now opens in the directory of the current used CSS file [#11597](https://github.com/JabRef/jabref/pull/11597)
 
 ### Fixed
 

src/main/java/org/jabref/gui/preferences/general/GeneralTabViewModel.java

@@ -66,7 +66,8 @@ public class GeneralTabViewModel implements PreferenceTabViewModel {
 
     private final BooleanProperty themeSyncOsProperty = new SimpleBooleanProperty();
 
-    private final StringProperty customPathToThemeProperty = new SimpleStringProperty();
+    // init with empty string to avoid npe in accessing
+    private final StringProperty customPathToThemeProperty = new SimpleStringProperty("");
 
     private final BooleanProperty fontOverrideProperty = new SimpleBooleanProperty();
     private final StringProperty fontSizeProperty = new SimpleStringProperty();
@@ -334,10 +335,14 @@ public StringProperty customPathToThemeProperty() {
     }
 
     public void importCSSFile() {
+
+        String fileDir = customPathToThemeProperty.getValue().isEmpty() ? preferences.getInternalPreferences().getLastPreferencesExportPath().toString()
+                : customPathToThemeProperty.getValue();
+
         FileDialogConfiguration fileDialogConfiguration = new FileDialogConfiguration.Builder()
                 .addExtensionFilter(StandardFileType.CSS)
                 .withDefaultExtension(StandardFileType.CSS)
-                .withInitialDirectory(preferences.getInternalPreferences().getLastPreferencesExportPath()).build();
+                .withInitialDirectory(fileDir).build();
 
         dialogService.showFileOpenDialog(fileDialogConfiguration).ifPresent(file ->
                 customPathToThemeProperty.setValue(file.toAbsolutePath().toString()));