yep

Gameboard.ShogiUI.Sockets/Repositories/GameboardRepository.cs

@@ -241,8 +241,12 @@ namespace Gameboard.ShogiUI.Sockets.Repositories
         logger.LogError(new InvalidOperationException(result.warning), result.warning);
         return null;
       }
-
-      return new Models.User(result.docs.Single().Name);
+      var userDocument = result.docs.SingleOrDefault();
+      if (userDocument != null)
+      {
+        return new Models.User(userDocument.Name);
+      }
+      return null;
     }
   }
 }