**Steps to replicate the issue** (include links if applicable):
* Login on a wiki with the Popups extension installed
* Go to your user settings ( appearance tab ) https://de.wikipedia.org/wiki/Special:Preferences#mw-prefsection-rendering
* Disable Page Previews but enable Reference Previews
* Visit an article page with references and hover a reference
**What happens?**:
* Reference Preview is not showing
**What should have happened instead?**:
* Reference Preview should show
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There's a sanity check in the code to make sure that we stop initializing the extension and the code bails out if there are no selectors configured:
https://gerrit.wikimedia.org/g/mediawiki/extensions/Popups/+/694b96a19f0673d936ad9257e9f42155ae8d0b47/src/index.js#256
But reference previews seems to register correctly with:
https://gerrit.wikimedia.org/g/mediawiki/extensions/Popups/+/694b96a19f0673d936ad9257e9f42155ae8d0b47/src/preview/model.js#241
Still when the check is done the selectors are empty. So I guess there's somewhat of a race condition happening.