The guild emblem is optional

[Sejsel]

There are quite a few guilds that have no emblem in the API, for example: https://api.guildwars2.com/v2/guild/bd558153-0f8e-e911-81a8-cde2ac1eed30

{
  "id": "BD558153-0F8E-E911-81A8-CDE2AC1EED30",
  "name": "Aomi",
  "tag": "Aomi"
}

The Emblem value is defaulted to an emblem with values of 0, but more importantly the Flags do not work correctly. An InvalidCastException is thrown when getting Gw2Sharp.WebApi.V2.Models.ApiFlags.List in this case.

To reproduce:

static async Task Main(string[] args)
{
	var client = new Gw2Client();
	var guild = await client.WebApi.V2.Guild["bd558153-0f8e-e911-81a8-cde2ac1eed30"].GetAsync();
	Console.WriteLine(guild.Emblem.Flags.List);
}

Exception:

Unhandled Exception: System.InvalidCastException: Unable to cast object of type 'System.Collections.Generic.List`1[Gw2Sharp.WebApi.V2.Models.ApiEnum]' to type 'System.Collections.Generic.IReadOnlyList`1[Gw2Sharp.WebApi.V2.Models.ApiEnum`1[Gw2Sharp.WebApi.V2.Models.GuildEmblemFlag]]'.
   at Gw2Sharp.WebApi.V2.Models.ApiFlags`1.get_List()
   at Gw2SharpTest.Program.Main(String[] args) in /tmp/Gw2SharpTest/Gw2SharpTest/Program.cs:line 13
   at Gw2SharpTest.Program.<Main>(String[] args)

[Archomeda]

Ah. I never thought that a guild wouldn't have the guild emblem set. I'll make that nullable.

Regarding the ApiFlags. It would seem that it's a side effect when constructing the default. I'll see if I can get rid of the base non-generic ApiFlags and ApiEnum, as these seem to be causing the issue.