fix: Add empty role list if not present (#1871)

src/Discord.Net.WebSocket/Entities/Users/SocketGuildUser.cs

@@ -125,12 +125,16 @@ namespace Discord.WebSocket
         {
             var entity = new SocketGuildUser(guild, guild.Discord.GetOrCreateUser(state, model.User));
             entity.Update(state, model);
+            if (!model.Roles.IsSpecified)
+                entity.UpdateRoles(new ulong[0]);
             return entity;
         }
         internal static SocketGuildUser Create(SocketGuild guild, ClientState state, PresenceModel model)
         {
             var entity = new SocketGuildUser(guild, guild.Discord.GetOrCreateUser(state, model.User));
             entity.Update(state, model, false);
+            if (!model.Roles.IsSpecified)
+                entity.UpdateRoles(new ulong[0]);
             return entity;
         }
         internal void Update(ClientState state, MemberModel model)