Bugfix in search gateway for topbar search

What does this MR do?

Fixes a bug from !1522 (merged) that happens if the "teaser" for a search result is null. This probably happens if the user did not set a city.

https://sentry.io/share/issue/ab5c88322d954ed9be58e56932785846/

https://sentry.io/share/issue/69a1c6de50e04a56a7b39d282d07afde/

How confident are you it won't break things if deployed?

Quite sure, seems to fix the problem on localhost

How to test

Steps a reviewer can take to verify that this MR does what it says it does e.g.

1. Checkout branch locally
2. Remove the city for any user in the database
3. Login as foodsaver
4. Search for the user from point 3 in the topbar
5. You should see the user without a teaser

Checklist

• added a test, or explain why one is not needed/possible...
• no unrelated changes
• asked someone for a code review
• joined #foodsharing-beta channel at https://slackin.yunity.org
• added an entry to CHANGELOG.md (description, merge request link, username(s))
• Once your MR has been merged, you are responsible to update the #foodsharing-beta Slack channel about what has been changed here. They will test your work in different browsers, roles or other settings