Fix navigation bar color in slideshow viewer

app/lib/widget/slideshow_viewer.dart

@@ -118,9 +118,15 @@ class _WrappedSlideshowViewerState extends State<_WrappedSlideshowViewer>
   Widget build(BuildContext context) {
     return Theme(
       data: buildDarkTheme(context),
-      child: const Scaffold(
+      child: const AnnotatedRegion<SystemUiOverlayStyle>(
+        value: SystemUiOverlayStyle(
+          systemNavigationBarColor: Colors.black,
+          systemNavigationBarIconBrightness: Brightness.dark,
+        ),
+        child: Scaffold(
           body: _Body(),
         ),
+      ),
     );
   }
 }