[BottomSheetDialogFragment + BottomNavigationView] weird behavior on navigation

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**Description:**
I've got a menu with 4 items (Home, Search, Categories and Plus), the Plus item is the `BottomSheetDialogFragment`, whenever I click on it, it makes me navigate back to my `startDestination` (which is Home) and open the `BottomSheetDialogFragment`.

**Expected behavior:**
Open the `BottomSheetDialogFragment` on the screen I'm actually at.

**Source code:**
```kotlin
val host: NavHostFragment = supportFragmentManager
.findFragmentById(R.id.nav_host_fragment) as NavHostFragment? ?: return
val navController = host.navController
val toolbar = findViewById(R.id.toolbar)
val appBarConfiguration = AppBarConfiguration(
setOf(
R.id.homeFragment,
R.id.searchFragment,
R.id.categoriesFragment,
R.id.plusFragment
))

setSupportActionBar(toolbar)

val bottomNav = findViewById(R.id.bottom_nav_view)
bottomNav?.setupWithNavController(navController)
```

**Android API version:** 19

**Material Library version:** 1.2.0-alpha06

**Device:** Galaxy S3 Neo 4.4.2

**Additional Note**:

When I remove `R.id.plusFragment` from appBarConfiguration and use:
```kotlin
findViewById(R.id.plusFragment).setOnClickListener {
navController.navigate(R.id.plusFragment)
}
```
the `BottomSheetDialogFragment` is displaying correctly in the fragment I'm currently at.

Start by reproducing the navigation flow with BottomNavigationView.setupWithNavController, NavHostFragment, AppBarConfiguration, and the BottomSheetDialogFragment on the stated Android API and Material Library versions. Compare the configured plusFragment item with the provided custom click-listener workaround. Done means the bottom sheet opens over the currently selected destination without returning to home.

Written by the indexing model from the issue text.