fix: fill energy deposition for Geant4OpticalTracker

[c-dilks]

Fix #1067

I'm not sure if this is the correct way to fix this, but it does restore the energy deposition distribution for the OpticalTracker example. In particular:

• does hit->truth need to be filled too?
• step->GetTotalEnergyDeposit() in the print statement is still always zero (but hit->energyDeposit looks correct)

BEGINRELEASENOTES

• fix: fill energy deposition for Geant4SensitiveAction<Geant4OpticalTracker>

ENDRELEASENOTES

[MarkusFrankATcernch]

Hi,
Thanks for spotting this!

If I trace the changes down, then the difference in the energy deposit for optical photons in the OpticalTracker SD is:
-- BAD: h.deposit() aka G4Step::GetTotalEnergyDeposit()
-- GOOD: deposit from MC contribution: deposit = (h.trackDef() == G4OpticalPhoton::OpticalPhotonDefinition()) ? h.trkEnergy() : h.totalEnergy();
where totalEnergy = GetTotalEnergyDeposit and trkEnergy = track->GetTotalEnergy()
which of course makes a difference.

Is this correct ?
If YES, then one could do quite some optimization here, because the SD callback Geant4SensitiveAction<Geant4OpticalTracker>::process() does the same calculations
as Geant4HitData::extractContribution(...), which is called in addition.

[c-dilks]

Is this correct ?

I'm not sure. @wdconinc spent some time working on this SD action, so perhaps he could comment.