URL: https://fr.wikipedia.org/wiki/Wikip%C3%A9dia:Accueil_principal
Browser / Version: Firefox 55.0
Operating System: Windows 10
Problem type: Something else - I'll add details below

Steps to Reproduce

1. Navigate to: https://fr.wikipedia.org/wiki/Wikip%C3%A9dia:Accueil_principal
2. Click on the lens icon of the search bar
3. Click on "Add Wikipédia (fr)"

Expected Behavior:

Wikipédia (fr) should get added to the search bar engines list

Actual Behavior:

Wikipédia (fr) does not get into the search bar engines list. It evens messes with my actual Firefox (standard release) search engines list.

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