I download the code of official Moodle mobile 2.7 from github (https://github.com/moodlehq/moodlemobile-phonegapbuild) and convert it through Phonegap Build without any changes. Then I open the mobile app with the Moodle site URL of my institution. I find that if a module page includes an empty folder, the module content are not visible on mobile app, as can be seen below. Neither the list of sections on the left nor the section content on the right is shown. If I delete the empty folder, the content is shown again.
My institution uses Moodle 2.8. We also install Moodle mobile additional feature plugin for the Moodle mobile app.
I convert Moodle mobile app 2.0, 2.2 and 2.5 before. All of these versions do not have problems when visiting module pages with empty folders when visiting my institution Moodle site.
I also add an empty folder in a module page in Moodle official demo site (http://school.demo.moodle.net/), the module page can be shown in the mobile app. I do not know whether it is because the demo site is under Moodle 3 and does not use Moodle mobile additional plugin.
It is a essential bug since many teachers leave empty folders in the module pages. And it is a big problem for students when their module page is not visible on the mobile app. I plan to upgrade the mobile app for my institution soon, since the Moodle site URL pre-populating function is quite important for us. I really hope the bug can be fixed as soon as possible.