(potentially) fixed object disposed issue with semaphore

fix random issue where we were trying to reset a session for a player that has not fully connected

Plugins/Stats/Helpers/StatManager.cs

@@ -1072,7 +1072,7 @@ namespace IW4MAdmin.Plugins.Stats.Helpers
             foreach (var stat in sv.GetClientsAsList()
                 .Select(_client => _client.GetAdditionalProperty<EFClientStatistics>(CLIENT_STATS_KEY)))
             {
-                stat.StartNewSession();
+                stat?.StartNewSession();
             }
         }