Don't perform logo search by default on logo search page

[raphael0202]

On https://hunger.openfoodfacts.org/logos/search, the following HTTP request is sent automatically: https://robotoff.openfoodfacts.org/api/v1/images/logos/search/?count=25&random=true

This is a very heavy request for the DB, as , as we perform a double join over 2 tables to get the number of items without any filtering. It would be better not to send any request when the page load, and wait for the user to provide input.