Remove null collections

src/Discord.Net.Rest/Entities/Interactions/RestApplicationCommand.cs

@@ -65,7 +65,7 @@ namespace Discord.Rest
 
             Options = model.Options.IsSpecified
                 ? model.Options.Value.Select(x => RestApplicationCommandOption.Create(x)).ToImmutableArray()
-                : null;
+                : ImmutableArray.Create<RestApplicationCommandOption>();
         }
 
         /// <inheritdoc/>

src/Discord.Net.Rest/Entities/Interactions/RestApplicationCommandOption.cs

@@ -62,11 +62,11 @@ namespace Discord.Rest
 
             Options = model.Options.IsSpecified
                 ? model.Options.Value.Select(x => Create(x)).ToImmutableArray()
-                : null;
+                : ImmutableArray.Create<RestApplicationCommandOption>();
 
             Choices = model.Choices.IsSpecified
                 ? model.Choices.Value.Select(x => new RestApplicationCommandChoice(x)).ToImmutableArray()
-                : null;
+                : ImmutableArray.Create<RestApplicationCommandChoice>();
         }
         #endregion