Fixed a few reference bugs with private messages

src/Discord.Net/Helpers/Reference.cs

@@ -32,7 +32,7 @@ namespace Discord
 				if (v == null && _id != null)
 				{
 					v = _getItem(_id);
-					if (v != null)
+					if (v != null && _onCache != null)
 						_onCache(v);
 					_value = v;
 				}

src/Discord.Net/Models/Channel.cs

@@ -79,7 +79,7 @@ namespace Discord
 				x => x.AddChannel(this), 
 				x => x.RemoveChannel(this));
 			_recipient = new Reference<User>(recipientId, 
-				x => _client.Users[x, _server.Id], 
+				x => _client.Users.GetOrAdd(x, _server.Id), 
 				x =>
 				{
 					Name = "@" + x.Name;

src/Discord.Net/Models/Message.cs

@@ -145,8 +145,19 @@ namespace Discord
 		internal Message(DiscordClient client, string id, string channelId, string userId)
 			: base(client, id)
 		{
-			_channel = new Reference<Channel>(channelId, x => _client.Channels[x], x => x.AddMessage(this), x => x.RemoveMessage(this));
-			_user = new Reference<User>(userId, x => _client.Users[x]);
+			_channel = new Reference<Channel>(channelId,
+				x => _client.Channels[x],
+				x => x.AddMessage(this),
+				x => x.RemoveMessage(this));
+			_user = new Reference<User>(userId,
+				x =>
+				{
+					var channel = Channel;
+					if (!channel.IsPrivate)
+						return _client.Users[x, channel.Server.Id];
+					else
+						return _client.Users[x, null];
+				});
 			Attachments = _initialAttachments;
 			Embeds = _initialEmbeds;
 		}