GM not working in Firefox 81.0.2 with DuckDuckGo Privacy Essentials extension

[brentfraser]

But it works if in FF I turn off the DuckDuckGo Privacy Essentials extension.

Symptom
Using the demo GM stops after it shows the basic HTML and does not show the Catalog entries.

Investigation
After I switch the index.html to use geomoose.js instead of geomoose.min.js, the FF console shows an error in GM's index.js line 94

    for (var i = 0; i < scriptTags.length; i++) {
        var src = scriptTags[i].getAttribute('src');
        if (src.indexOf('geomoose.js') >= 0 || src.indexOf('geomoose.min.js') >= 0) {
            distPath = src.split('/').slice(0, -1).join('/');
        }
    }

The error is at the if(src.indexof because the first of the three scriptTags[] does not have a 'src' attribute so src is null. While the other two scriptTags[] look legit (gemoose.js and config.js), this bit of JavaScript looks odd. It's about 25 lines of things like Object.defineProperty(navigator, "doNotTrack", { value: "unspecified" }); (Thanks, Privacy Essentials extension!)

Fix
Anyways, the fix is to test if src is not null prior to the (src.indexOf test.

[klassenjs]

Is the DDG extension injecting an anonymous script into the page? That seem like an odd thing to do and a bit of a difficult environment to target/test if the browser is rendering a different page than we coded.

However, adding the null check in the name of defensive programming seems like a good thing to do.

if(src && src.indexof...

[brentfraser]

Those were my thoughts too. I think there is a pitched battle between sites trying to harvest info about users and browsers/users trying to prevent it.

And like you say, we need to code to expect the unexpected.