fix(source): resolve compilation error in filter dialog

Corrects a compilation error in `filter_dialog.dart` by adding the required `logoUrl` parameter to the `Source` constructor within an `orElse` block. This dummy object is used as a fallback and now aligns with the updated `Source` model.

Author: fulleni

lib/content_management/widgets/filter_dialog/filter_dialog.dart

@@ -264,6 +264,7 @@ class _FilterDialogState extends State<FilterDialog> {
                         name: '',
                         description: '',
                         url: '',
+                        logoUrl: '',
                         sourceType: SourceType.other,
                         language: Language(
                           id: '',