Dont send nickname in User.Edit unless one is specified

src/Discord.Net/API/Client/Rest/UpdateMember.cs

@@ -22,7 +22,7 @@ namespace Discord.API.Client.Rest
         public ulong? VoiceChannelId { get; set; }
         [JsonProperty("roles"), JsonConverter(typeof(LongStringArrayConverter))]
         public ulong[] RoleIds { get; set; }
-        [JsonProperty("nick", DefaultValueHandling = DefaultValueHandling.Ignore), DefaultValue("")]
+        [JsonProperty("nick", NullValueHandling = NullValueHandling.Ignore)]
         public string Nickname { get; set; }
 
         public UpdateMemberRequest(ulong guildId, ulong userId)

src/Discord.Net/Models/User.cs

@@ -272,14 +272,17 @@ namespace Discord
             }
             if (!isCurrentUser || isMuted != null || isDeafened != null | voiceChannel != null || roles != null)
             {
-                if (nickname == "") nickname = Nickname;
+                //Swap "" and null. Our libs meanings and the API's are flipped.
+                if (nickname == null) nickname = "";
+                else if (nickname == "") nickname = null;
+
                 var request = new UpdateMemberRequest(Server.Id, Id)
                 {
                     IsMuted = isMuted ?? IsServerMuted,
                     IsDeafened = isDeafened ?? IsServerDeafened,
                     VoiceChannelId = voiceChannel?.Id,
                     RoleIds = roleIds,
-                    Nickname = nickname ?? ""
+                    Nickname = nickname
                 };
                 await Client.ClientAPI.Send(request).ConfigureAwait(false);
             }