FCS: Only simulate one hit if energy is negative

Former-commit-id: 3088d5920b46add53497e87e32a596d51d331a77

Simulation/ISF/ISF_FastCaloSim/ISF_FastCaloSimEvent/src/TFCSLateralShapeParametrizationHitNumberFromE.cxx

@@ -28,6 +28,10 @@ int TFCSLateralShapeParametrizationHitNumberFromE::get_number_of_hits(TFCSSimula
   int cs=calosample();
   double energy=simulstate.E(cs);
 
+  if (energy < 0) {
+    return 1;
+  }
+
   double sigma_stochastic=m_stochastic/sqrt(energy/1000.0);
   int hits = CLHEP::RandPoisson::shoot(simulstate.randomEngine(), 1.0 / (sigma_stochastic*sigma_stochastic + m_constant*m_constant));