refactor: return CataloggerError as Results instead of throwing in commands

Catalogger.Backend/Bot/Commands/IgnoreMessageCommands.Users.cs

@@ -94,7 +94,7 @@ public partial class IgnoreMessageCommands
         {
             var (userId, guildId) = contextInjection.GetUserAndGuild();
             if (!guildCache.TryGet(guildId, out var guild))
-                throw new CataloggerError("Guild was not cached");
+                return CataloggerError.Result("Guild not in cache");
 
             var guildConfig = await guildRepository.GetAsync(guildId);