title: NullPointerException on executing command on NavigationUI
body: <p>Cant find what causes the problem with null exception. Making the project by the guide and it doesnt have this problem. using the same libraries versions like in guidr.</p>
  <p>Error message</p>
  <pre><code>Attempt to invoke virtual method 'void androidx.appcompat.app.ActionBar.setTitle(java.lang.CharSequence)' on a null object reference
  Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.appcompat.app.ActionBar.setTitle(java.lang.CharSequence)' on a null object reference
  </code></pre>
  <pre><code>import androidx.appcompat.app.AppCompatActivity
  import android.os.Bundle
  import androidx.navigation.NavController
  import androidx.navigation.Navigation
  import androidx.navigation.ui.NavigationUI
  import androidx.navigation.ui.setupWithNavController
  import kotlinx.android.synthetic.main.activity_main.*
  
  class MainActivity : AppCompatActivity() {
  
      private lateinit var navController: NavController
      override fun onCreate(savedInstanceState: Bundle?) {
          super.onCreate(savedInstanceState)
          setContentView(R.layout.activity_main)
          navController = Navigation.findNavController(this, R.id.nav_host_fragment)
          bottom_nav.setupWithNavController(navController)
  
  
          NavigationUI.setupActionBarWithNavController(this, navController)
  
      }
  
      override fun onSupportNavigateUp(): Boolean {
          return NavigationUI.navigateUp( navController, null)
      }
  }
  </code></pre>