Default data set has missing data for Rechtsgebied and Instantie

[jvdzwaan]

The Rechtsgebied and Instantie dropdown boxes for the default dataset have an empty line. This is probably due to missing data. It would be better if the dropdown box said 'missing' or 'unknown' instead of having an empty line.

[dafnevk]

Easiest option is to change it in the default dataset

[dafnevk]

see commit 2fb0bfc