ConstructPageUrl function Null safety
Implementation
Future<String> ConstructPageUrl(String chapterId, String token,
String chapterHash, String filename, bool dataSaver) async {
var baseUrl = await getBaseUrl(chapterId);
var dataMode = dataSaver ? 'data-saver' : 'data';
return 'https://$baseUrl/$token/$dataMode/$chapterHash/$filename';
}