Why does an error occur when initializing tts in Android?

Question

Null error when initializing in tts I can't figure out why I'm getting the null error The error does not occur on my equipment, and when I check the log, symptoms sometimes appear even on the same type of device. Do you have any way to solve this problem? I've been thinking about this for a long time, but I can't find a solution

Maybe the problem is because tts is not installed? If so, is there a way to check if tts is installed?

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    ...

    tts = new TextToSpeech(this, new TextToSpeech.OnInitListener() {
        @Override
        public void onInit(int status) {
            if(status != TextToSpeech.ERROR)
            {
                try
                {
                    tts.setLanguage(Locale.getDefault()); // NullPointerException
                }
                catch(StringIndexOutOfBoundsException e)
                {
                    Log.i("debug","onInit e = " + e);
                }
            }

        }
    }, "com.google.android.tts");
}