Javascript does not work in offline mode

[pixeline]

I'm trying to make this online tool work offline too, as the content does not change often.
https://plancomptablebelge.be

When I test it on an Android 4.4.2 mobile phone, when I put it offline, the offline.html page shows up, but the javascript does not kick in.

Note that it is entirely possible that I didn't do everything right, it's the first time I use upup.js.
So, how I set it up:

File organisation:

/upup.js
/upup.sw.min.js
/index.html
/offline.html
/assets/...

In index.html

<script src="/assets/js/app-min.js?v={VERSION}"></script>
<script src="/upup.js"></script>
<script>
    UpUp.start({
      'content-url': 'offline.html', // show this page to offline users
      'assets': ['/assets/css/app.css', '/assets/js/app-min.js']
    });
</script>

in offline.html
<script src="/assets/js/app-min.js"></script>

Expected Behavior

On mobile in offline mode, the menu icon should reveal the in-page navigation menu.

Current Behavior

On mobile in offline mode, when clicking on the menu icon, nothing happens.

Your Environment

• Version used: 0.3.0
• Browser Name and version: chrome on android, latest
• Operating System and version (desktop or mobile): android 4.4.2 (mobile)
• Link to your project: https://plancomptablebelge.be

Thank you!

[TalAter]

There seems to be a problem with your upup.sw.min.js file.

It is trying to load https://plancomptablebelge.be/upup.sw.min.js but that file is empty... make sure you have the real file there and that your server serves it right.