pl-fe: fix reset to default theme

Signed-off-by: nicole mikołajczyk <git@mkljczk.pl>

packages/pl-fe/src/features/preferences/index.tsx

@@ -151,7 +151,7 @@ const Preferences = () => {
 
   const onThemeReset = () => {
     dispatch(changeSetting(['themeMode'], plFeConfig.defaultSettings.themeMode, { save: false }));
-    dispatch(changeSetting(['theme'], undefined, { showAlert: true }));
+    dispatch(changeSetting(['theme'], plFeConfig.defaultSettings.theme, { showAlert: true }));
   };
 
   const displayMediaOptions = React.useMemo(() => ({