Fragment : void android.view.View.unFocus(android.view.View) on a null object reference

Question

Since the crash is coming from internal library of android and the most suspected code is below, this crash is coming in Oreo devices only

ChatAlertDialogFragment chatAlertDialogFragment = ChatAlertDialogFragment.getInstance(bundle);
chatAlertDialogFragment.show(getFragmentManager(), ChatAlertDialogFragment.class.getSimpleName());

NOTE: When we replace simple fragment manager with the support fragment manger then it works fine.

This is the exception log

07-18 14:59:45.103 E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.aspiringminds.amcat.debug, PID: 13679
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.unFocus(android.view.View)' on a null object reference
        at android.view.ViewGroup.removeViewInternal(ViewGroup.java:5207)
        at android.view.ViewGroup.removeViewAt(ViewGroup.java:5170)
        at android.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1561)
        at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1611)
        at android.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2204)
        at android.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2148)
        at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2049)
        at android.app.FragmentManagerImpl$1.run(FragmentManager.java:718)
        at android.os.Handler.handleCallback(Handler.java:789)
        at android.os.Handler.dispatchMessage(Handler.java:98)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6541)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)

ChatAlertDialogFragment class code

public class ChatAlertDialogFragment extends DialogFragment {
  public static ChatAlertDialogFragment getInstance(Bundle bundle) {
    ChatAlertDialogFragment chatAlertDialogFragment = new ChatAlertDialogFragment();
    chatAlertDialogFragment.setCancelable(false);
    chatAlertDialogFragment.setArguments(bundle);
    return chatAlertDialogFragment;
  }

  @Override
  public Dialog onCreateDialog(Bundle savedInstanceState) {
    super.setStyle(android.R.style.Theme_Holo_Light_Dialog_MinWidth, android.R.style.Theme_Holo_Light_Dialog_MinWidth);
    Dialog dialog = super.onCreateDialog(savedInstanceState);
    dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
    dialog.setCanceledOnTouchOutside(false);
    dialog.setCancelable(false);
    return dialog;
  }
}