Getting error: java.lang.RuntimeException: An error occurred while executing doInBackground()

I got an error when running the application, and when I saw the error like the title above and went to the code below.

    @SuppressLint("StaticFieldLeak")
private class getList extends AsyncTask<String, String, List<ModList>> {
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected void onPostExecute(List<ModList> modLists) {
        super.onPostExecute(modLists);

        adapter.updateList(modLists);

    }

    @RequiresApi(api = Build.VERSION_CODES.KITKAT)
    @Override
    protected List<ModList> doInBackground(String... strings) {

        List<ModList> parseList = new ArrayList<>();

        parseList = DataHandler.ParsingJSON(mContext, strings[0]);

        return parseList;
    }
}