if timeToEvent and timeToTreatmentSwitch are empty they cause error
Created by: marek05
As for me (Estonian MAITT database) the target cohort counts were very low (<20 persons) then the timeToEvent and timeToTreatmentSwitch made the code crash as the minimum count is 30 and therefore the timeToEvent and timeToTreatmentSwitch elements were empty. I added checks to check the number rows in these elements and log info that the elements are empty instead of crashing the code.