Resolve "Mailing lists api fails without boards"

Wouter Doeland
2019-10-03T17:23:44+02:00

Closes #842 #### Previous behaviour Steps to reproduce: 1. Start a local server with no boards (thalia.nu has the same problem, but it already has boards so it can't be reproduced there). 2. Go to /api/v1/mailinglists/ #### New behaviour Steps to validate that it works: (Same as above) 1. Start a local server with no boards (thalia.nu has the same problem, but it already has boards so it can't be reproduced there). 2. Go to /api/v1/mailinglists/