Fix search bug caused by previous fixes

What does this MR do?

Set $regionToSearch to mixed to allow more flexible inputs. Should fix both Sentry errors below. Might not need a changelog as it was only broken on beta for a short time.

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

Should work as it was working before

Links to related issues

• !1206 (comment 252868506)
• https://sentry.io/organizations/foodsharing-ev/issues/1366039516/?project=1400917
• https://sentry.io/organizations/foodsharing-ev/issues/1366039518/?project=1400917

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