fix warning

mobile/lib/routing/gallery_guard.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:auto_route/auto_route.dart';
 import 'package:immich_mobile/routing/router.dart';
 
@@ -13,12 +15,14 @@ class GalleryGuard extends AutoRouteGuard {
       // Replace instead of pushing duplicate
       final args = resolver.route.args as GalleryViewerRouteArgs;
 
-      router.replace(
-        GalleryViewerRoute(
-          renderList: args.renderList,
-          initialIndex: args.initialIndex,
-          heroOffset: args.heroOffset,
-          showStack: args.showStack,
+      unawaited(
+        router.replace(
+          GalleryViewerRoute(
+            renderList: args.renderList,
+            initialIndex: args.initialIndex,
+            heroOffset: args.heroOffset,
+            showStack: args.showStack,
+          ),
         ),
       );
       // Prevent further navigation since we replaced the route