handle getLocation null response properly

Session::getLocation returns null in case there is no valid location available. Have all paths using this a proper handling. This sometimes doesn't make sense, but it is better than failing the request leading to a lot of errors in production.

e.g.

• https://sentry.io/organizations/foodsharing-ev/issues/904373266/?project=1400913&query=is%3Aunresolved
• or just try accessing https://foodsharing.network/essenskoerbe/find without a session :-)