[Adaptive] `getProperty` prebuilt function or dynamic index does not work

@boydc2014 @luhan2017

Our Todo bot sample uses this approach and this does not work in master.

The goal is that we need this -

user.lists = {
    "todo": [
        "one", 
        "two"
    ],
    "shopping": [],
    "generic": []
}

The following C# code does not work -

var rootDialog = new AdaptiveDialog(nameof(AdaptiveDialog))
{
    Generator = new TemplateEngineLanguageGenerator(),
    Triggers = new List<OnCondition>()
    {
        new OnConversationUpdateActivity()
        {
            Actions = WelcomeUserAction()
        },
        new OnIntent() {
            Intent = "GetUserProfile",
            Actions = new List<Dialog>() {
                new InitProperty() {
                    Property = "user.lists",
                    Type = "object"
                },
                new SetProperty() {
                    Property = "$listName",
                    Value = "'todo'"
                },
                new InitProperty() {
                    // Alternatively getProperty(user.lists, $listName) does not work either
                    Property = "user.lists[$listName]",
                    Type = "array"
                },
                new EditArray() {
                    // Alternatively getProperty(user.lists, $listName) does not work either
                    ItemsProperty = "user.lists[$listName]",
                    Value = "'one'",
                    ChangeType = EditArray.ArrayChangeType.Push
                },
                new SendActivity() {
                    Activity = new ActivityTemplate("I have '{join(user.lists[$listName], ', ')}'")
                }
            }
        }
    }
};

Expected:

    I have 'one'

Actual:

      Exception caught : Error occurs when evaluating expression $join(user.lists[$listName], ', '): user.lists[$listName] evaluates to  which is not a list.

[luhan2017]

I verified in Tom’s branch, it is working now.

[tomlm]

#2818 PR is out