PM 12001 - Fix Empty User Search 500 (#4770)

* Setting null if user2Fa is empty. Added null check to view as well.

* Not setting the temp data at all if empty.

src/Admin/Controllers/UsersController.cs

@@ -66,7 +66,12 @@ public class UsersController : Controller
 
         if (_featureService.IsEnabled(FeatureFlagKeys.MembersTwoFAQueryOptimization))
         {
-            TempData["UsersTwoFactorIsEnabled"] = await _twoFactorIsEnabledQuery.TwoFactorIsEnabledAsync(users.Select(u => u.Id));
+            var user2Fa = (await _twoFactorIsEnabledQuery.TwoFactorIsEnabledAsync(users.Select(u => u.Id))).ToList();
+            // TempDataSerializer is having an issue serializing an empty IEnumerable<Tuple<T1,T2>>, do not set if empty.
+            if (user2Fa.Count != 0)
+            {
+                TempData["UsersTwoFactorIsEnabled"] = user2Fa;
+            }
         }
 
         return View(new UsersModel

src/Admin/Views/Users/Index.cshtml

@@ -73,7 +73,9 @@
                             @if (featureService.IsEnabled(Bit.Core.FeatureFlagKeys.MembersTwoFAQueryOptimization))
                             {
                                 var usersTwoFactorIsEnabled = TempData["UsersTwoFactorIsEnabled"] as IEnumerable<(Guid userId, bool twoFactorIsEnabled)>;
-                                @if(usersTwoFactorIsEnabled.FirstOrDefault(tuple => tuple.userId == user.Id).twoFactorIsEnabled)
+                                var matchingUser2Fa = usersTwoFactorIsEnabled?.FirstOrDefault(tuple => tuple.userId == user.Id);
+
+                                @if(matchingUser2Fa is { twoFactorIsEnabled: true })
                                 {
                                     <i class="fa fa-lock fa-lg fa-fw" title="2FA Enabled"></i>
                                 }