Trending nav item is repeating in header

Steps to reproduce:

1. Go to https://github.com/sindresorhus/refined-github It’s added twice
2. Click on a sub-repo navigation item - e.g. Issues tab.

This has been introduced relatively recently on master.

[fregante]

I’d rather not do that because it’d push the real problem under the rug, deprioritizing the issue. You don’t want an extension to run 10 times.

[busches]

An easy way to work around this is to add the same code we have for most other items we add to the dom and check for it’s existence before adding it. Doesn’t solve the root cause of why the extension is running twice, but if it’s an odd edge case, it may be worth the time savings of solving it the quick and easy way, especially since we use that pattern for everything else.