159135253: Trigger FirebaseInAppMessagingClickListener. messageClicked when action is empty

## What feature would you like to see?
Invoke FirebaseInAppMessagingClickListener.messageClicked for use case when you don't want to trigger browser intent and you are interested only to handle other data (such as key-value map defined in the campaign)

As a user, I don't want to trigger any URL specific browser intent when i click my In App Message popup. I want to trigger below code without any side effects:

```val inAppMessaging = Firebase.inAppMessaging
inAppMessaging.addClickListener { inAppMessage, action ->
// invoke only code inside
val data = inAppMessage.data // I am only interested in that data, don't want to trigger any browser intent
}
```

Unfortunately, this listener is not being invoked when the defined action is empty. You must define the action with proper URL to be able to trigger this listener when popup is clicked.

Can we trigger such listener always when the popup is being clicked, even when the defined action for campaign is empty?