refactor per code review

Author: rustdesk

flutter/lib/web/bridge.dart

@@ -1539,12 +1539,12 @@ class RustdeskImpl {
   Future<void> mainAccountAuth(
       {required String op, required bool rememberMe, dynamic hint}) {
     // Safari only allows auth popups while handling the original user gesture.
-    // Call into JS synchronously so the web OIDC flow can pre-open the window.
-    js.context.callMethod('setByName', [
+    // Use Future.sync so the JS call runs synchronously (pre-opening the OIDC
+    // window) while any interop error still surfaces as a Future error.
+    return Future.sync(() => js.context.callMethod('setByName', [
           'account_auth',
           jsonEncode({'op': op, 'remember': rememberMe})
-        ]);
-    return Future.value();
+        ]));
   }
 
   Future<void> mainAccountAuthCancel({dynamic hint}) {