Core/AuctionHouse: Fixes collection was modified errror. Also fixes mail not having the right subject.

Source/Game/AuctionHouse/AuctionManager.cs

@@ -24,6 +24,7 @@ using Game.Mails;
 using Game.Network.Packets;
 using System;
 using System.Collections.Generic;
+using System.Collections.Concurrent;
 
 namespace Game
 {
@@ -426,14 +427,9 @@ namespace Game
 
         public bool RemoveAuction(AuctionEntry auction)
         {
-            bool wasInMap = AuctionsMap.Remove(auction.Id) ? true : false;
-
             Global.ScriptMgr.OnAuctionRemove(this, auction);
 
-            // we need to delete the entry, it is not referenced any more
-            auction = null;
-
-            return wasInMap;
+            return AuctionsMap.TryRemove(auction.Id, out AuctionEntry removedItem);
         }
 
         public void Update()
@@ -570,7 +566,7 @@ namespace Game
             return AuctionsMap.LookupByKey(id);
         }
 
-        Dictionary<uint, AuctionEntry> AuctionsMap = new Dictionary<uint, AuctionEntry>();
+        ConcurrentDictionary<uint, AuctionEntry> AuctionsMap = new ConcurrentDictionary<uint, AuctionEntry>();
     }
 
     public class AuctionEntry
@@ -761,12 +757,12 @@ namespace Game
 
         public string BuildAuctionMailSubject(MailAuctionAnswers response)
         {
-            return $"{itemEntry}:0:{response}:{Id}:{itemCount}";
+            return $"{itemEntry}:0:{(uint)response}:{Id}:{itemCount}";
         }
 
         public static string BuildAuctionMailBody(ulong lowGuid, ulong bid, ulong buyout, ulong deposit, ulong cut)
         {
-            return string.Format($"{lowGuid}:{bid}:{buyout}:{deposit}:{cut}");
+            return $"{lowGuid}:{bid}:{buyout}:{deposit}:{cut}";
         }
 
         // helpers