Fixed permission cache errors when adding a channel

src/Discord.Net/Models/Channel.cs

@@ -107,6 +107,11 @@ namespace Discord
             : this(client, id)
         {
             Server = server;
+            if (server != null)
+            {
+                foreach (var user in server.Users)
+                    AddUser(user);
+            }
         }
         internal Channel(DiscordClient client, ulong id, User recipient)
             : this(client, id)

src/Discord.Net/Models/Server.cs

@@ -204,7 +204,8 @@ namespace Discord
         #region Channels
         internal Channel AddChannel(ulong id)
         {
-            var channel = _channels.GetOrAdd(id, x => new Channel(Client, x, this));
+            var channel = new Channel(Client, id, this);
+            channel = _channels.GetOrAdd(id, x => channel);
             Client.AddChannel(channel);
             return channel;
         }