Route unknown paths back to map

lib/app/router/app_router.dart

@@ -17,6 +17,7 @@ class AddExperienceArgs {
 
 GoRouter createAppRouter() {
   return GoRouter(
+    errorBuilder: (context, state) => const MapflowShell(),
     routes: [
       GoRoute(
         path: '/',
@@ -25,7 +26,13 @@ GoRouter createAppRouter() {
           GoRoute(
             path: 'experience/new',
             pageBuilder: (context, state) {
-              final args = state.extra as AddExperienceArgs;
+              final extra = state.extra;
+              final args = extra is AddExperienceArgs
+                  ? extra
+                  : const AddExperienceArgs(
+                      coordinate: null,
+                      hasTelegramAuth: true,
+                    );
               return CustomTransitionPage<void>(
                 fullscreenDialog: true,
                 key: state.pageKey,