Minor UI fixes to memories (#1719)

lib/ui/home/memories/full_screen_memory.dart

@@ -153,6 +153,7 @@ class _FullScreenMemoryState extends State<FullScreenMemory> {
     final inheritedData = FullScreenMemoryData.of(context)!;
     final showStepProgressIndicator = inheritedData.memories.length < 60;
     return Scaffold(
+      backgroundColor: Colors.black,
       extendBodyBehindAppBar: true,
       appBar: AppBar(
         toolbarHeight: 84,

lib/ui/home/memories/memory_cover_widget.dart

@@ -221,6 +221,7 @@ class _MemoryCoverWidgetState extends State<MemoryCoverWidget> {
         child: ThumbnailWidget(
           memory.file,
           shouldShowArchiveStatus: false,
+          shouldShowSyncStatus: false,
           key: Key("memories" + memory.file.tag),
         ),
       ),