#323 Ensure that VN Multiple primitives always send a list of tagged VN IDs

[chrismarget-j]

The API for VN Multiple primitives don't like when we omit the slice of VN IDs, nor when we send null.

This change ensures we send an empty list even when the caller supplies a nil slice.

Also snuck in here:

• a bug fix in the new format checking script: loop used wrong variable file rather than f
• formatting to an offending file which tripped up the format checking script

Closes #323