Minor Cleanup

src/Discord.Net/DiscordClient.cs

@@ -926,8 +926,9 @@ namespace Discord
                                 //Logger.Verbose($"Presence Updated: {server.Name}/{user.Name}");
                                 OnUserPresenceUpdated(user);
                             }
-                            else
-                                Logger.Warning("PRESENCE_UPDATE referenced an unknown user.");
+                            /*else
+                                Logger.Warning("PRESENCE_UPDATE referenced an unknown user.");*/
+                                //This happens when users leave a server
                         }
                         break;
                     case "TYPING_START":

src/Discord.Net/Models/Server.cs

@@ -409,16 +409,19 @@ namespace Discord
             {
                 foreach (var channel in AllChannels)
                     channel.RemoveUser(id);
+                return member.User;
             }
-            return member.User;
+            return null;
         }
 
         /// <summary> Gets the user with the provided id and is a member of this server, or null if not found. </summary>
         public User GetUser(ulong id)
         {
             Member result;
-            _users.TryGetValue(id, out result);
-            return result.User;
+            if (_users.TryGetValue(id, out result))
+                return result.User;
+            else
+                return null;
         }
         /// <summary> Gets the user with the provided username and discriminator, that is a member of this server, or null if not found. </summary>
         public User GetUser(string name, ushort discriminator)