Fix to Correctly Render Production.Rundir in Templates

Currently, from a fresh initialisation, if {{ production.rundir }} is included in an outside template file it will be rendered as None instead of how it should be. It would seem to be that this caused by a missing return in the rundir property of the Analysis class. This MR adds that return which corrects this behaviour by adding this return which brings this case into line with the other two possible cases.