The previous version would trigger sub-pipelines (LTE-2x2, ...) if no MR
had the NSA tag (without a commit, etc). Of course, this would make all
pipelines subsequently fail (as not enough arguments, such as the
commit, were given). In this commit, we read the output of `jq` from
JSON, which will result in an empty list if no MR is tagged with the NSA
label (and the output in the console will be nicer as well).