Kotlin Android Extensions nullability

SampleFragment.kt

import kotlinx.android.synthetic.main.fragment_main.*

class SampleFragment : Fragment() {

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                              savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment_main, container, false)
    }
    override fun onDestroy() {
        super.onDestroy()
        Log.d("kotlinx", "onDestroy textView ID: " + textView.id)
    }
}