ktools Empty loss stream cause run

Issue Description

Occasionally run_ktools.sh hangs when there is one or more empty pipes. The cause appears to be when summarycalc receives an empty loss stream. It is an intermittent problem, sometimes the script completes successfully even if some pipes loss streams are empty.

This is more likely to happen;

When there are more processes than events in the model run (e.g. a multi-core machine with a single event model)
When there are many events that do not cause a loss to the portfolio and they all coincide in a single pipe

Part of the solution is setting the number of parallel processes appropriately for the run. However, there will still be plausible cases where no losses are generated in a whole pipe (the portfolio is very small, or low risk, or there is a high loss threshold applied to losses). This bug needs to be fixed so that the script always completes, even though some pipes may not contribute any losses to outputs.