Handle measures with 0 events

[LFISHER7]

This job request is an example where no patients are returned for a chosen measure. In this case it was due to the wrong codelist type being specified for one of the codelists, but there will be cases where this happens even if the codelists are correctly specified.

As we can't conditionally run actions easily within the yaml, we'll need to handle this case for each action and produce the outputs of these actions, even if they're empty. We can add a flag to the action that generates the report to allow something sensible to be rendered.

To the user, this will look like a successful run, and it will trigger an output check/release. We should consider whether we want to flag the analysis as unsuccessful at an earlier stage