Buttons in Selector item not updating text color after hiding activity indicator

**Problem Description:**
I followed [this suggestion](https://github.com/alexaubry/BulletinBoard/issues/50#issuecomment-370392843) to show the activity indicator as soon as a selector item (e.g `PetSelectorBulletinPage`) is displayed, by using `shouldStartWithActivityIndicator = true` and implementing `presentationHandler`.

After hiding the activity indicator, however, the two buttons under description aren't responding to touches, i.e. their text color isn't refreshing after calling `setTitleColor`.

I think the bug could be related to [this line](https://github.com/alexaubry/BulletinBoard/blob/db62747228ba4a3d2e58c15c718c3deeaf15af6e/Sources/BLTNItemManager.swift#L273), specifically the parameter `elementsChanged` being false in function call. However I couldn't find the exact issue preventing buttons from refreshing correctly. Any help is appreciated.

**Steps to reproduce:**
I created a sample project demonstrating the issue that can be downloaded [here](https://github.com/alexaubry/BulletinBoard/files/2389519/BLTNBoardBug.zip).
Relevant portion of code:

```
enum BulletinDataSource {

static func makeChoicePage() -> PetSelectorBulletinPage {
let page = PetSelectorBulletinPage(title: "Choose your Favorite")
page.descriptionText = "Your favorite pets will appear when you open the app."
page.actionButtonTitle = "Select"

// BUG: Uncomment the following lines to make buttons unresponsive to UI updates
/*
page.shouldStartWithActivityIndicator = true
page.presentationHandler = { item in
item.manager?.hideActivityIndicator()
}
*/
return page
}
}

```

**Environment:**
- Device: Simulator
- OS: iOS 11.4
- Version of BulletinBoard: 2.0.2 (latest)