bug: duplicated slash in uuid

e.g. https://pfp-api.acdh-ch-dev.oeaw.ac.at/place//000fcb52-a14a-4c33-8916-06cad914a3f8

should be https://pfp-api.acdh-ch-dev.oeaw.ac.at/place/000fcb52-a14a-4c33-8916-06cad914a3f8 to be resolvable