handle default.txt changelog in fdroid metadata/

fixup !1240

fdroidserver/update.py

@@ -998,6 +998,7 @@ def insert_localized_app_metadata(apps):
                                               os.path.join(root, f))
                 elif f == 'default.txt':
                     # use "default.txt" changelog entry as fallback.
+                    locale = segments[-2]
                     localized = _get_localized_dict(apps[packageName], locale)
                     if not localized.get('whatsNew', ''):
                         _set_localized_text_entry(apps[packageName], locale, 'whatsNew',