Fix potential division by zero in BacktestingResultHandler
Fix potential division by zero in BacktestingResultHandler

This can happen with algorithms that do not call AddSecurity and have a non-security benchmark such as SetBenchmark(x => 0)

QuantConnect/Lean,AnshulYADAV007/Lean,Jay-Jay-D/LeanSTP,QuantConnect/Lean,AnshulYADAV007/Lean,kaffeebrauer/Lean,AlexCatarino/Lean,redmeros/Lean,redmeros/Lean,JKarathiya/Lean,StefanoRaggi/Lean,AlexCatarino/Lean,kaffeebrauer/Lean,AnshulYADAV007/Lean,StefanoRaggi/Lean,jameschch/Lean,jameschch/Lean,AlexCatarino/Lean,AnshulYADAV007/Lean,AlexCatarino/Lean,redmeros/Lean,QuantConnect/Lean,JKarathiya/Lean,kaffeebrauer/Lean,jameschch/Lean,Jay-Jay-D/LeanSTP,StefanoRaggi/Lean,redmeros/Lean,StefanoRaggi/Lean,Jay-Jay-D/LeanSTP,QuantConnect/Lean,kaffeebrauer/Lean,jameschch/Lean,kaffeebrauer/Lean,Jay-Jay-D/LeanSTP,JKarathiya/Lean,jameschch/Lean,Jay-Jay-D/LeanSTP,JKarathiya/Lean,AnshulYADAV007/Lean,StefanoRaggi/Lean